MAP602_Experimental Psychology

Sensory Processes: Structure and Function of Gustatory and Kinesthetic 145 illusion results in a mismatch between how heavy an object looks and how heavy the muscles \"think\" it should be. In general, larger objects are judged as being heavier than smaller objects of the same weight. The kinesthetic sense does not mediate equilibrium, or sense of balance. Balance involves different sensory pathways and originates in large part within the inner ear. Kinesthesis also referred to as kinesthesia, is the perception of body movements. It involves being able to detect changes in body position and movements without relying on information from the five senses. You are using your kinesthetic sense whenever you are involved in a physical activity such as walking, running, driving, dancing, swimming and anything that requires body movement. 5.9 Key Words/Abbreviations  The Gustatory System: The gustatory system is the sensory system responsible for the perception of taste and flavor.  Gustatory Perception: Gustatory perception is one of the five traditional senses that belongs to the gustatory system.  Taste Buds and Papillae of the Tongue: In the human body, a stimulus refers to a form of energy which elicits a physiological or psychological action or response.  Sweetness: Sweetness is produced by the presence of sugars.  Sourness: Sourness is acidity.  Bitterness: TAS2R38 are responsible for the human ability to taste bitter substances.  Pungency: Substances such as ethanol and capsaicin cause a burning sensation.  Astringency: Some foods, such as unripe fruits, contain tannins or calcium oxalate that cause an astringent or puckering sensation.  Structure and Function of Gustatory: The gustatory cortex is located in cerebral cortex, which is the outer part of the brain.  Structure and Function of Kinesthetic: Kinesthetic handwriting training takes the drudgery out of a task that is often difficult and time-consuming. CU IDOL SELF LEARNING MATERIAL (SLM)

146 Experimental Psychology  Kinesthesis: The kinesthetic sense does not mediate equilibrium.  Learning Styles: Kinesthesis relates to one of the three major learning styles in Fleming VAK model. 5.10 Learning Activity 1. You are required to prepare a live project report on “The Gustatory System of Human Body”. _________________________________________________________________ _________________________________________________________________ 2. You are suggested to identify the elements related to the structure and function of gustatory. _________________________________________________________________ _________________________________________________________________ 3. You are required to prepare the report on “Structure and Function of Kinesthetic”. _________________________________________________________________ _________________________________________________________________ 5.11 Unit End Exercises (MCQs and Descriptive) A. Descriptive Type Questions 1. Explain in details about the gustatory system of Human Body. 2. What is Gustatory? Explain in details about the gustatory perception. 3. Discuss about functional structure. 4. Explain about taste buds and papillae of the tongue. 5. Discuss in details about structure and function of gustatory. 6. Explain about structure and function of kinesthetic. 7. Write note on: Kinesthesis and Learning Styles. CU IDOL SELF LEARNING MATERIAL (SLM)

Sensory Processes: Structure and Function of Gustatory and Kinesthetic 147 B. Multiple Choice Questions 1. Which of the following is the sensory system responsible for the perception of taste and flavor? (a) Gustatory system (b) Olfactory system (c) Visual system (d) All the above 2. Which of the following is one of the five traditional senses that belong to the gustatory system? (a) Sweetness (b) Sourness (c) Saltiness (d) All the above 3. Which of the following is a form of chemoreception which occurs in the specialized taste receptors in the mouth? (a) Taste (b) Choice (c) Beauty (d) None of the above 4. Which of the following is located in cerebral cortex? Which is the outer part of the brain? (a) The gustatory cortex (b) The Kinesthetic (c) The kinesthetic sense (d) All the above 5. The ability to assess the weight of an object is another function of __________. (a) Kinesthesia (b) The gustatory cortex (c) The kinesthetic sense (d) All the above Answers: 1. (a), 2. (d), 3. (a), 4. (a), 5. (a) 5.12 References References of this unit have been given at the end of the book.  CU IDOL SELF LEARNING MATERIAL (SLM)

148 Experimental Psychology UNIT 6 PERCEPTION Structure: 6.0 Learning Objectives 6.1 Introduction 6.2 The Concept of Perception 6.3 Nature of Perception 6.4 Need for Perception 6.5 Importance of Perception 6.6 Types of Perception 6.7 Process of Perception 6.8 Elements of Perception 6.9 Determinants of Perception 6.10 Difference between Perception and Sensation 6.11 Perceptual Organization 6.12 Perceptual Mechanism 6.13 Perception and itsApplication in Organizations 6.14 Interpersonal Perception 6.15 Perceptual Constancy CU IDOL SELF LEARNING MATERIAL (SLM)

Perception 149 6.10 Summary 6.11 Key Words/Abbreviations 6.12 LearningActivity 6.13 Unit End Exercises (MCQs and Descriptive) 6.14 References 6.0 Learning Objectives After studying this unit, you will be able to:  Discuss about perceptual process  Elaborate process of perception  Explain the perceptual organization 6.1 Introduction Perception is the process of attaining awareness or understanding of the environment by organizing and interpreting sensory information. All perception involves signals in the nervous system, which in turn result from physical stimulation of the sense organs. For example, vision involves light striking the retinas of the eyes, smell is mediated by odor molecules and hearing involves pressure waves. Perception is not the passive receipt of these signals, but can be shaped by learning, memory and expectation. Perception involves these “top- down” effects as well as the “bottom-up” process of processing sensory input. Perception depends on complex functions of the nervous system, but subjectively seems mostly effortless because this processing happens outside conscious awareness. 6.2 The Concept of Perception Perception is considered to be an intellectual process which involves in transforming sensory stimuli to meaningful information. Perception is the process of interpreting something that we see or hear in our mind. What we see and hear is later used to judge and give a judgment on a situation, person, group, thing, etc. CU IDOL SELF LEARNING MATERIAL (SLM)

150 Experimental Psychology People working in an organization differ in terms of physical characteristics such as age, sex, etc. background characteristics such as training and education and personality traits such as extroversion or aggressiveness. One of the consequences of such differences is that do not view the things in the same way. There is often difference of opinion and evaluation. People differ in their reaction due to the differences in perception they have about things. Perception is described as person’s view of reality. For example, a factory worker may discount most of what management says about devising sales, decreased profit margin, etc. Most of such talk is regarded by unions as an attempt by management to exploit the workers for its own gain. But shareholder may attribute decline sales and profit margin to insufficient utilization of resources. Perception is a process by which individuals organize and interprets their sensory impressions in order to give meaning to their environment. Perception is determined by both physiological and psychological characteristics of the human being whereas sensation is conceived with only the physiological features. Thus perception is not just what one sees with the eyes it is much more complex process by which an individual selectivity absorbs and organize the perceived information in a specific fashion and then interprets the information to make an assessment about what is going on in one’s environment. Meaning of Perception The word “perception” comes from the Latin words perceptio, percipio, which means “receiving, collecting, and action of taking possession, apprehension with the mind or senses.” “Perception is the process of attaining awareness or understanding of sensory information”. Perception is one of the oldest fields in psychology. The oldest quantitative law in psychology is the Weber-Fechner law, which quantifies the relationship between the intensity of physical stimuli and their perceptual effects. The study of perception gave rise to the Gestalt school of psychology, with its emphasis on holistic approach. Perception is the process by which an individual selects organizes and interprets stimuli into a meaningful and coherent picture of the world. Perception differs from individual to individual. It is the way a person sees the world around him. It is a personal phenomenon. CU IDOL SELF LEARNING MATERIAL (SLM)

Perception 151 “Perception is the process through which the information from outside environment is selected, received organized and interpreted to make it meaningful to us. This input of meaningful information results in decisions and actions which are taken by all individuals.” Definitions According to professors Schiffman and Kanuk, “Perception is the process by which an individual selects organizes and interprets stimuli into meaningful and coherent picture of the world”. According to Mr. Fred Luthans, “Perception is an important mediating cognitive process which persons make interpretation of the stimulus or situation they forced with.” According to Joseph Reitz, “Perception may be defined as a process by which individuals organize and interpret their sensory impressions in order to give meaning to their environment.” According to Joseph Reitz, “Perception includes all those processes by which an individual receives information about his environment seeing, hearing, feeling, tasting and smelling. The study of these perpetual processes shows that their functioning is affected by three classes of variables the objects or events being perceived, the environment in which perception occurs and the individual doing the perceiving.” According to Ajit Singh, “Perception refers to the interpretation of sensory data and the visual image what we see. This visual perception refers to interpreting the image of the external world projected on the retina of the eye and constructing a model of the three dimensional world.” 6.3 Nature of Perception “Perception refers to the interpretation of sensory data. It involves the sensation which detects the presence of a stimulus. Perception also involves understanding and finding out what the stimulus means”. For example, when we see something, the visual stimulus is regarded as the light energy which is reflected from the external world. Here our eyes become the sensor. This visual image what we see that is the external thing becomes perception. Further, when it is interpreted is done in the visual CU IDOL SELF LEARNING MATERIAL (SLM)

152 Experimental Psychology cortex of the brain. We can conclude that visual perception refers to interpreting the image of the external world projected on the retina of the eye and constructing a model of the three dimensional world. From this, we can conclude that perception is a little more than sensation. It interrelates, integrates and understands diverse sensations and information from many organs of the body by means of which a person identifies things and objects, the sensations refer to. Perception is mainly influenced by both physiological and psychological features of all individuals. But usually, sensation is conceived with only physiological characteristics. By this, it is clear that perception not only what we see but it is more complex process by which a human being takes in or observes all kinds of stimuli in the environment and his surroundings. He then cognitively organizes all the perceived information in a specific and desired manner and then interprets the information about what he feels is going on in the environment. It is regarded as a subjective process where different people may perceive the same environment in different ways based on the aspect of the situation. The way they interpret the situation and observe it is different in case of different people. Perception is considered to be an: (i) Perception is the intellectual process. (ii) Perception is the basic cognitive or psychological process. (iii) Perception becomes a subjective process and different people may perceive the same event differently. 6.4 Need for Perception One of the important cognitive factors of human behavior is perception. There can be no behavior without perception and perception lies at the base of every individual behavior. The beat supervisor is one who can accurately and precisely estimates employee’s perceptions and makes his moves. Unfortunately, a manager is not gifted with any set of rules, formula and techniques to understand others mind and perceptions. 1. Every one perceives the world and approaches the life problems differently. This factor is very important in understanding human behavior. The world as we see necessarily the CU IDOL SELF LEARNING MATERIAL (SLM)

Perception 153 same as it really is. It is because what we hear is not what is really said. We buy what we like best and not what is best. It is because of perception that the particular job may appear a good to one and bad to another. 2. Due to perceptions only “facts” as they are seen by one viewer may be different from the facts as seen by another viewer. The tension or discomfort that one feels when he thinks he is missing something others may not realize it. Everyone wears his own rose-colored glasses, that one does not always see what is actually happening. If people behave on the basis of their perceptions, then change behavior in a predetermined direction can be easier for understanding their present perception of the world. 3. People act as they perceive and different people perceive things differently. People’s perception is determined by their needs. Like the mirrors at an amusement park, they distort the world in relation to their tensions. 4. Perception is important dynamite for the manager who wants to avoid making errors when dealing with people and events in the work setting. This problem is made even more complicated by the fact that different people may perceive the same situation in different ways. A manager’s responses to a situation, for example may be misinterpreted by a subordinate who previewed the situation quite differently. In order to deal with the subordinates effectively, a manager must understand their perceptions properly. 6.5 Importance of Perception Perception is very important to understand and interpret human behavior which includes and helps us understand how different people perceive things in different manner. Individual’s behavior is mainly based on their perceptions of what reality is, not on reality itself. The world as it is perceived is a world that is important for understanding human behavior. The significance of perception is discussed under: 1. Each and every individual sees and approaches the world and handles different problems in the world and even reacts to them in a different manner. No two people think in the same manner. Whatever a person sees is not necessarily the same as it really is. This is mainly because what we hear is not what is really spoken by us, but what we actually perceive as CU IDOL SELF LEARNING MATERIAL (SLM)

154 Experimental Psychology being said. When we purchase something it is not because it is the best, but mainly because we take it to be the best for others. This is mainly because of perception. Another example which we can consider is the job satisfying power of an individual. One person may consider his job to be satisfying, the other be not be completely satisfied with his job this is mainly due to an individual’s perception. 2. If a group of people behave in the same way, we can predict their behavior in different circumstances by understanding their present perception of the environment. Two viewers generally view the same fact in different ways. 3. Perception helps in determining the needs of different individuals. This is mainly because each individual’s perception is influenced by their needs. No two people will have similar kinds of needs. 4. Perception is considered to be very important to all the managers who are working in an organization this is because this helps them in avoiding any kinds of errors when they deal with people or different events at their workplace. This problem becomes more complicated because different people view the same situation in different manners. In order to deal with their superiors and subordinates in the right manner, managers should understand their perceptions properly. 5. Perception is very important in an organization as well as it helps in understanding the tasks to be performed by an individual, understanding associated importance of tasks allotted, understanding preferred behavior to complete respective tasks and clarifying role perceptions. 6.6 Types of Perception Perception is divided into six types which include: 1. Perception of Sound: It is considered to be the ability to receive sound by identifying different vibrations. 2. Perception of Speech: It is the competence of interpreting and understanding the sounds of language which is heard. CU IDOL SELF LEARNING MATERIAL (SLM)

Perception 155 3. Perception of Touch: It includes identifying objects and things through patterns of its surface by touching it and feeling them. 4. Perception of Taste: It is the ability to receive flavor of substances by tasting it through sensory organs known as taste buds. 5. Perception of Other Senses: They help in approving the perception through body, which includes balance, acceleration, pain, time, sensation felt in throat and lungs, etc. 6. Perception of the Social World: It permits people to understand other individuals and groups of their social world. 6.7 Process of Perception Perception is a process of receiving, selecting organizing, interpreting, checking and reacting to stimuli. This is like an input-through put-output process in which the stimuli can be considered as ‘inputs’ transformation of ‘input’ through selection organization and interpretation as ‘throughputs’ and the ultimate action as ‘output’. Perceptual process is the different levels of perception which an individual goes through. The different levels include: Step-1: Receiving Receiving is the first and most important stage in the process of perception. It is the initial stage in which a person collects all information and receives the information through the sense organs. Whatever information he gets he collects it and stores the required information. This information can be received from various sources. It is a physiological aspect of perception process. Step-2: Selecting Selecting is the second stage in the process. Here, a person does not receive the data randomly but selectively. A person selects some information out of all in accordance with his interest or needs. Others are screened out. The selection of data is dominated by various external and internal factors. External factors: The factors that influence the perception of an individual externally are intensity, size, contrast, movement, repetition, familiarity and novelty. Internal factors: The factors that influence the perception of an individual internally are psychological requirements, learning, background, experience, self-acceptance and interest. CU IDOL SELF LEARNING MATERIAL (SLM)

156 Experimental Psychology Normally, an individual will select the objects which interest him and will avoid that for which he is indifferent. This is also called 'selective perception'. Step-3: Organizing Keeping things in order or say in a coordinated way is organizing. In order to make sense of the data received, it is important to organize them. There are three ways by which the data which is selected is organized. We can organize the data by: (i) Grouping them on the basis of their similarity, proximity, closure and continuity. For example, all the workers coming from the same place may be perceived as similar on the basis of proximity. (ii) Establishing a figure ground is the basic process in perception. Here by figure, we mean what is kept as main focus and by ground we mean background stimuli, which are not given attention. When people get incomplete information, they tend to fill up the gaps themselves to make the information more meaningful. (iii) Perceptual constancy that is the tendency to stabilize perception so that contextual changes do not affect them. This is called as simplification. Step-4: Interpreting Finally, data is interpreted which means forming an idea about a particular object depending upon the need or interest. Interpretation means that the information we have sensed and organized is finally given a meaning by turning it into something that can be categorized. It includes stereotyping, halo effect, etc. 6.8 Elements of Perception The elements of perception are as follows: 1. Sensation Sensation refers to the immediate response to received stimuli. Stimulus is any unit of input to any of the senses. A stimulus generally includes products, packages, brand names, advertisement and commercials. The sensory receptions are the human organ which includes eyes, nose, ears, CU IDOL SELF LEARNING MATERIAL (SLM)

Perception 157 mouth and skin which receive sensory inputs and the sensory functions are to see, hear, smell, taste and feel. Both these two factors, i.e., sensory inputs and sensory functions might response either singly or jointly in the process of evaluating the decision-making. Sensitivity to stimuli depends on the individual’s sensory receptors and the extent of stimuli to which one is exposed. Sensation also depends on the differentiation of the input also. It is also depends on the intensity of the sensory input, which may or may not provide sensation at all. In case in the decrease of sensory input, the process of detecting the input or intensity increases so that maximum sensitivity can be attain under minimal situation. 2. The Absolute Threshold The lowest level where sensation can be attained is called the absolute threshold. If a person is being able to detect any difference between something and nothing, it is called the absolute threshold for their particular stimulus. The adaptation indicates on refers to specially getting used to some sensation which in turn being accommodated to a certain level of stimulation. Sensory adoption does not remain same all the time. So, they advertise according to needs and wants of the customers. This is mainly done in order to attract customers, so that their products are being noticed. 3. The Differential Threshold The minimal difference which can be detected or can be found out between two similar stimuli is called differential threshold. This is also as jnd (just noticeable difference). According to Ernst Weber, jnd between two stimuli was not an absolute amount but an amount relative to the intensity of the first stimulus. According to Weber’s law, the stronger the initial stimulus, the greater the additional intensity needed for the second stimulus to be perceived as different. Weber’s law holds for all the senses and for almost all intensities. 4. Subliminal Perception The stimulus which is too weak or too brief to be consciously seen or heard is not so strong enough which may be perceived by one or more receptor cells. This is known as subliminal perception because the stimulus is below the threshold though not obviously below the absolute threshold of the receptors involved. CU IDOL SELF LEARNING MATERIAL (SLM)

158 Experimental Psychology 6.9 Determinants of Perception Following three factors influence the perception: 1. Perceiver When an individual looks at the object and attempts to interpret the same, what he or she sees it is largely influenced by the personal characteristics. Perception is a matter of attitude that can be positive or negative. Some workers would feel and perceive that the prevailing working conditions in the organizations are congenial for work and it contributes positively while for others, it would be inadequate and demand improvement. This is indicative of positive and negative attitude patterns. The major characteristics of the perceiver influencing perception are: (a) Attitudes: The perceiver’s attitudes affect perception. For example, Mr. X is interviewing candidates for a very important position in his organization—a position that requires negotiating contracts with suppliers, most of whom are male. Mr. X may feel that women are not capable of holding their own in tough negotiations. This attitude with doubt affect his perceptions of the female candidates he interviews. (b) Moods: Moods can have a strong influence on the way perceive someone. We think differently when we are happy than we do when we are depressed. In addition, we remember information that is consistent with our mood state better than information that is inconsistent with our mood state. When in a positive mood, we form more positive impressions of other. When in a negative mood, we tend to evaluate others unfavorably. (c) Motives: Unsatisfied needs or motives stimulate individuals and may exert a strong influence on their perceptions. For example, in an organizational context, a boss who is insecure perceives a subordinate’s efforts to do an outstanding job as a threat to his or her own position. Personal insecurity can be translated into the perception that others are out to “get my job”, regardless of the intention of the subordinates. (d) Self-concept: Another factor that can affect social perception is the perceiver’s self- concept. An individual with a positive self-concept tends to notice positive attributes in another person. In contrast, a negative self-concept can lead a perceiver to pick out negative CU IDOL SELF LEARNING MATERIAL (SLM)

Perception 159 traits in another person. Greater understanding of self allows us to have more accurate perceptions of others. (e) Interest: The focus of our attention appears to be influenced by our interests. Because our individual interests differ considerably, what one person notices in a situation can differ from what other perceive. For example, the supervisor who has just been reprimanded by his boss for coming late is more likely to notice his colleagues coming late tomorrow than he did last week. (f) Cognitive structure: Cognitive structure, an individual's pattern of thinking, also affects perception. Some people have a tendency to perceive physical traits, such as height, weight and appearance, more readily. Cognitive complexity allows a person to perceive multiple characteristics of another person rather than attending to just a few traits. (g) Expectations: Finally, expectations can distort your perceptions in that you will see what you expect to see. Some specific characteristics of the perceiver reveal (i) Knowing oneself makes it easier to see others accurately. (ii) One's own characteristics affect the characteristics one is likely to see in other. (iii) People who accept themselves are more likely to be able to see favourable aspects of other people. (iv) Accuracy in perceiving others is not a single skill. The above four characteristics greatly influence how a person perceives other in the environmental situation. 2. Situation Change in situation leads to incorrect perception about a person. Time is one factor, which influences the perception. Time is related to work setting and social setting. A person decked up for party may not be noticeable but the same dress in office would be noticed distinctly, though the person has not changed. What is important to remember is the perception should be done in a correct manner not to be led due to work setting or social setting and that the situation is not allowed to perceive wrongly. An object can be identified by its size, shade, shape, sound it makes and CU IDOL SELF LEARNING MATERIAL (SLM)

160 Experimental Psychology background. It can be distinguished based on its movement. In darkness, it may be identified by its silhouette, for example, caravan moving on skyline at the dawn. The situation in which the interaction between the perceiver and the target takes place has an influence on the perceiver’s impression of the target. The strength of the situational cues also affects social perception. Some situations provide strong cues as to appropriate behavior. In this situation, we assume, i.e., individual’s behavior can be accounted for by the situation and that it may not reflect the individual’s disposition. 3. Objective/Target Verbal Communication from targets also affects our perception of them. Non-verbal communication conveys a great deal of information about the target. The perceiver deciphers eye contact, facial expressions, body movements and posture all in an attempt to form an impression of the target. 6.10 Difference between Perception and Sensation Sensation is the response of a physical sensory organ. The physical senses are touch, vision, hearing, smell and taste. These senses are affected by stimuli continuously. The stimuli may be both internal and external to the human body and reaction in particular sense organ takes place because of these. Examples of sensation may be reaction of eye to color, ear to sound and so on. Perception is something more than sensation. It correlates, integrates and comprehends diverse sensations and information from many organs of the body by means of which a person identifies things and objects the sensation relates to. Perception classifies the stimuli based on past experience feeling and motives. Thus, perception is determined by both physiological and psychological characteristics of the organism. However, sensation only activates the organs of the body and is not affected by psychological factors as learning and motives. The following statement further clarifies the difference between the two. “By means of my eye, I see, but am not eye who see and tend to see an object in its totality, a thing or event with certain qualities, with a figure and from set against a background”. Sensation and perception plays two complimentary but totally different roles in how we interpret the world around us. Sensation is a state of heightened interest or emotion and perception is insight, intuition or knowledge gained by perceiving Sensation is the process by which we sense our CU IDOL SELF LEARNING MATERIAL (SLM)

Perception 161 environment through touch, sight, taste and smell. This raw information from our sensory organs is then transmitted to the brain where perception is made. Perception is our way of interpreting what these sensations mean and how to make sense of it. Sensory abilities are measure by the absolute threshold, which the weakest level of stimulus that can be accurately detected. For humans, this could be a candle seen 30 miles away on dark, clear night or the scent of a drop of perfume in a large room. The stimuli come from receptors in our bodies which are located in our eyes, ears, nose, skin, muscles and even in the certain parts of our digestive tract. These receptors are designed to detect certain types of physical energy, such as light and sound waves. Stimulation is then converted to electrochemical signals called neural impulses, which the nervous system transmits to the different regions of the brain’s cortex. The different regions of the cortex translate different neural impulses into different psychological experiences. During perception, the brain computes the size and distance relationship, determines where edges and boundaries exist and identify figures. The brain automatically computes the sensory feedback and guides the body to perform the necessary task. When our perception of an object is distracted, our calculations pertaining to size and distance are also affected. Our previous experiences and what we expect to see or not to see contributes a lot to our perception of things around us. 6.11 Perceptual Organization Perceptual organization is the process of grouping visual elements together (organization) so that one can more readily determine the meaning of the visual as a whole (perception). If you think about the main screen of Microsoft Word, you have buttons along the top which represent commands or actions, text in the middle which is what you are writing, and messages along the bottom which indicate status. Similar items are grouped together, making it easy to understand their basic purpose. This idea holds true for all of the applications in the Microsoft Office suite and many Windows- based applications. Perception is tempered by point of view and experience. Because of this, no two people see things the same way if left to their own devices. One person might see a fancy sports car and another might see an accident waiting to happen. One person might see a cell phone as a necessary CU IDOL SELF LEARNING MATERIAL (SLM)

162 Experimental Psychology communications device and another might see the same device as a time waster. And while one person might see a random set of paint brush strokes, another might see a masterpiece. Our perception is governed by the information we have access to and the way we interpret it. That is why the area of perceptual organization is so important. 6.12 Perceptual Mechanism Perceptual mechanism consists of three sub-processes, viz., selection organization and interpretation. Once the sense organs detect a stimulus in the environment, a person selects organizes and interprets it through perceptual selectivity, perceptual organization and perceptual interpretation. Put together, these are known as perceptual mechanisms. Perceptual selection or perceptual selectivity refers to a tendency within a person to select one or a few out of the many stimuli present in the environment; this selectivity is based on one’s demographic, socio-cultural and psychographic factors. A person would tend to select those stimuli that appear relevant and attractive to him. Perceptual organization refers to the process of organizing the various stimuli with other cues around so that a whole picture can be created. In other words, the various stimuli are organized and given a form. It is the process of organizing inputs into a definite, coherent and interpretable structure. Perceptual interpretation refers to the process of drawing in inferences out of the organized whole and giving meaning to it. 6.13 Perception and its Application in Organizations People in organizations are always assessing others. Managers must appraise their subordinate’s performance, evaluate how co-workers are working. When a new person joins a department, he or she is immediately assessed by the other persons. These have important effect on the organization. 1. Employment Interview Interviewers make perceptual judgments that are often inaccurate. Different interviewers see different things in the same candidate and arrive at different conclusions about the applicant. CU IDOL SELF LEARNING MATERIAL (SLM)

Perception 163 Employment interview is an important input into the hiring decision and perceptual factors influence who is hired and vis-à-vis the quality of an organization’s labour force. 2. Performance Appraisals An employee’s performance appraisal is very much dependent on the perceptual process. An employee’s future is closely tied to his or her appraisal – promotions, increments and continuation of employment are among the common outcomes. The performance appraisal represents an assessment of an employee’s work. While this may be objective most jobs are evaluated in subjective terms. Subjective measures are judgmental. The evaluator forms a general impression of an employee’s work, to the degree that managers use subjective measures in appraising employee’s the evaluator perceives to be ‘good or bad’ employee characteristics/s will significantly influence the appraisal outcome. 3. Assessing Level of Effort In many organizations, the level of an employee’s effort is given high importance. Assessment of an individual’s effort is a subjective judgment susceptible to perceptual distortions and bias. 4. Assessing Loyalty Another important judgment that managers decide about employees is whether they are loyal to the organization. 6.14 Interpersonal Perception Interpersonal perception is the process of making meaning from people and relationship interact with in our daily lives. We sometimes look at others in a way that they are not. Our perception towards our peers is different from our bosses or people with high authorities. We tend to judge people so quickly base on our perception which makes it not fair for the people we are judging. We usually select a certain aspect of a person and base our perception about that person without even thinking. CU IDOL SELF LEARNING MATERIAL (SLM)

164 Experimental Psychology Interpersonal perception is an area of research in social psychology which examines the beliefs that interacting people has about each other. This area differs from social cognition and person perception by being interpersonal rather than interpersonal and thus requiring the interaction of at least two actual people. Another important point about the process of interpersonal perception is that normal social interaction is basically conservation, social norms operate to preserve existing interaction patterns and perceptions. Sociologist Erving Goffoan had described the tendency of people to preserve the ‘face’ that others present to them when someone acts ‘Out of character’ social pressures are mobilized to force him back in his role. In social situations, we tend to act in such a way that we maintain our own self-image and the self-image we see others presenting. We resist telling someone that he has egg on his chain because we assume that this is not part of the image he wants to present and we do not want him to ‘loss face’ and be embarrassed. This conservative interaction norm tends to decrease the accuracy of interpersonal perception by relinquishing opportunities to test the accuracy of our perceptions of others. The norm tends to decrease the accuracy of interpersonal perception by relinquishing opportunities to test the accuracy of our perceptions of others. The norm dictates that we cannot frankly tell others our impressions of them if these impressions differ from the fact they are presenting. If someone presents himself as a leader, it is hard to tell him you do not feel like following. Thus, we are denied information about others’ true thoughts and feelings by the face we present. A theoretical conceptualization of this process we can be depicted in the following manner, called the Johari Window named after Joe Luft and Harry in roam. Applications of Interpersonal Perception in the Organization 1. Employment interview: A major step into who is hired or rejected is the employment interview. Interviewers generally draw early impressions that become very quickly entrenched. If negative information is exposed early in the interview, it tends to be more heavily weighted than if that same information were conveyed later. CU IDOL SELF LEARNING MATERIAL (SLM)

Perception 165 2. Performance evaluation: An employee’s future is closely tied to his or her appraisal – promotions, pay raises and continuation of employment are among the most obvious outcomes. The performance evaluation represents an assessment of an employee’s work. 3. Employee effort: An individual future in an organization is usually not dependent on performance alone. In many organizations, the level of an employee’s effort is given high performance. 4. Employee loyalty: Another important judgment that managers make about employees is whether they are loyal to the organization. Few organizational appreciate employees, especially those in the managerial ranks. Some may see an employee who questions a top management decision as disloyal, yet caring and concerned by others. 6.15 Perceptual Constancy Perceptual constancy refers to the tendency to perceive an object you are familiar with as having a constant shape, size and brightness despite the stimuli changes that occur. Suppose you are at a neighborhood bus stop with a friend. Example You see the bus as it turns the corner a few blocks away. From a distance, the bus looks like a mere dot in your field of vision. You put up your palm and notice that you can cover the entire area of the bus with your palm. As the bus approaches the stop, it begins to take up more and more of your field of vision. Your palm no longer covers the area of the bus. By the time the bus reaches the stop, you realize that the bus is twice as tall as you. Despite the fact that the bus now takes up a majority of your field of vision, you do not perceive the bus as having grown. You know that the bus has the same size, rectangular shape and brightness now as it did when you saw it in the distance. The reason you know this is due to perceptual constancy. Perceptual Constancy – Shape and Size Perceptual constancy perceives objects as having constant shape, size and color regardless of changes in perspective, distance and lighting. CU IDOL SELF LEARNING MATERIAL (SLM)

166 Experimental Psychology Fig. 6.1: Perceptual Constancy Size constancy is when people’s perception of a particular object’s size does not change regardless of changes in distance from the object, even though distance affects the size of the object as it is projected onto the retina. Shape constancy is when people’s perception of the shape of an object does not change regardless of changes to the object’s orientation. Distance constancy refers to the relationship between apparent distance and physical distance: it can cause us to perceive things as closer or farther away than they actually are. Color constancy is a feature of the human color perception system that ensures that the color of an object is perceived as similar even under varying conditions. Auditory constancy is a phenomenon in music, allowing us to perceive the same instrument over differing pitches, volumes and timbres, as well as in speech perception, when we perceive the same words regardless of who is speaking them. Barriers to Perceptual Constancy Human beings make objectives and goals for achievement of the task of the organization. Human being judgments are regarding their organization environment and its location. Either success or failure depends on the perceptual accuracy of judgment and its effect on organization. Efforts CU IDOL SELF LEARNING MATERIAL (SLM)

Perception 167 and decisions are valuable contingency towards upon the accuracy of the information as well as the accuracy of impressions. 1. Stereotyping • It refers to the tendency to assign attributes to someone solely on the basis of the category of people, of which that person is a member. • It is one of the most common barriers in accurately perceiving others. • It is involved judging someone on the basis of one’s perception of the group to which that person belongs. • The tendency is to ascribe positive or negative characteristics to others on the basis of general categorizations and perceived similarities. • It means simplifying the process of perception and making judgments of other people, instead of dealing with a range of complex and alternative stimuli. 2. Halo Effect It refers to the tendency of judging the person entirely on the basis of a single trait which either favorable or unfavorable. It refers to one trait forms a general impression either positive or negative. It is also likely to be related to our self-image. It is a process whereby a person’s perception is formed on the basis of a single favorable trait or impression. It tends to shut out other relevant characteristics of a person. It combines information based on the category or class to which a person, situation or object belongs. It strongly impacts at the organization stage. It occurs when one attribute of a person or situation is used to develop an overall impression of the individual or situation. It is likely to occur in the organization stage. 3. Expectancy It refers to tendency to perceive people, objects or events on the basis of what we expected them to be in the first place. It may create certain things in the work situations which an individual can be expected to do. It is also known as self-fulling prophecy. It is expecting certain things to happen and will shape the behavior of the perceiver in such a way that the expected is more likely CU IDOL SELF LEARNING MATERIAL (SLM)

168 Experimental Psychology to happen. The tendency to create or in another situation is also called the “Pygmalion effect.” It is to be either positive or negative outcomes. Managers should adopt positive and optimistic approaches to people at workplace in an organization. 4. Perceptual Defense It refers to the tendency for people to protect themselves against ideas, objects or situations that are threatening. It is the mental process by which people tend to protect themselves from stimuli which are emotionally disturbing or perceptually threatening. It tends to distort either ignore information or stimuli which are culturally unacceptable or in the conflict with our established beliefs. 5. Projection It refers to the tendency for people to see their own traits in others. It deals with the assignment of one’s personal attributes to other individuals. It is likely to occur in interpretation stage in an organization. Projection can be controlled through a high degree of self-awareness and empathy towards an organization. It refers to be attributing one’s own characteristics to other people. 6.16 Summary Perception is the process of attaining awareness or understanding of the environment by organizing and interpreting sensory information. All perception involves signals in the nervous system, which in turn result from physical stimulation of the sense organs. For example, vision involves light striking the retinas of the eyes, smell is mediated by odor molecules and hearing involves pressure waves. Perception is not the passive receipt of these signals, but can be shaped by learning, memory and expectation. Perception involves these “top- down” effects as well as the “bottom-up” process of processing sensory input. Perception depends on complex functions of the nervous system, but subjectively seems mostly effortless because this processing happens outside conscious awareness. Perception is very important to understand and interpret human behavior which includes and helps us understand how different people perceive things in different manner. Individual’s behavior is mainly based on their perceptions of what reality is, not on reality itself. The world as it is perceived is a world that is important for understanding human behavior. CU IDOL SELF LEARNING MATERIAL (SLM)

Perception 169 One of the important cognitive factors of human behavior is perception. There can be no behavior without perception and perception lies at the base of every individual behavior. The beat supervisor is one who can accurately and precisely estimates employee’s perceptions and makes his moves. Unfortunately, a manager is not gifted with any set of rules, formula and techniques to understand others mind and perceptions. Sensation refers to the immediate response to received stimuli. Stimulus is any unit of input to any of the senses. A stimulus generally includes products, packages, brand names, advertisement and commercials. The sensory receptions are the human organ which includes eyes, nose, ears, mouth and skin which receive sensory inputs and the sensory functions are to see, hear, smell, taste and feel. Both these two factors, i.e., sensory inputs and sensory functions might response either singly or jointly in the process of evaluating the decision–making. Sensitivity to stimuli depends on the individual’s sensory receptors and the extent of stimuli to which one is exposed. Sensation also depends on the differentiation of the input also. It also depends on the intensity of the sensory input, which may or may not provide sensation at all. In case in the decrease of sensory input, the process of detecting the input or intensity increases so that maximum sensitivity can be attain under minimal situation. The lowest level where sensation can be attained is called the absolute threshold. If a person is being able to detect any difference between something and nothing, it is called the absolute threshold for their particular stimulus. The adaptation indicates on refers to specially getting used to some sensation which in turn being accommodated to a certain level of stimulation. Sensory adoption does not remain same all the time, so they advertise according to needs and wants of the customers. This is mainly done in order to attract customers, so that their products are being noticed. Perceptual organization is the process of grouping visual elements together (organization) so that one can more readily determine the meaning of the visual as a whole (perception). If you think about the main screen of Microsoft Word, you have buttons along the top which represent commands or actions, text in the middle which is what you are writing and messages along the bottom which indicate status. Similar items are grouped together, making it easy to understand their basic purpose. This idea holds true for all of the applications in the Microsoft Office suite and many Windows- based applications. CU IDOL SELF LEARNING MATERIAL (SLM)

170 Experimental Psychology Perceptual mechanism consists of three sub-processes, viz., selection organization and interpretation. Once the sense organs detect a stimulus in the environment, a person selects organizes and interprets it through perceptual selectivity, perceptual organization and perceptual interpretation. Put together, these are known as perceptual mechanisms. Perceptual selection or perceptual selectivity refers to a tendency within a person to select one or a few out of the many stimuli present in the environment; this selectivity is based on one’s demographic, socio-cultural and psychographic factors. A person would tend to select those stimuli that appear relevant and attractive to him. Perceptual organization refers to the process of organizing the various stimuli with other cues around so that a whole picture can be created. In other words, the various stimuli are organized and given a form. It is the process of organizing inputs into a definite, coherent and interpretable structure. Perceptual constancy refers to the tendency to perceive an object you are familiar with as having a constant shape, size and brightness despite the stimuli changes that occur. Suppose you are at a neighborhood bus stop with a friend. 6.17 Key Words/Abbreviations  Perception: Perception is the process of attaining awareness.  Nature of Perception: “Perception refers to the interpretation of sensory data.  Importance of Perception: Perception is very important to understand and interpret human behavior.  Need for Perception: One of the important cognitive factors of human behavior is perception.  Perception of Speech: It is the competence of interpreting and understanding the sounds of language which is heard.  Perception of Taste: It includes identifying objects and things through patterns of its surface by touching it and feeling them.  Process of Perception: Perception is a process of receiving, selecting organizing, interpreting, checking and reacting to stimuli. CU IDOL SELF LEARNING MATERIAL (SLM)

Perception 171  Sensation: Sensation refers to the immediate response to received stimuli.  Subliminal Perception: The stimulus which is too weak or too brief to be consciously seen or heard is not so strong.  Perceiver: When an individual looks at the object and attempts to interpret the same.  Perceptual Organization: Perceptual organization is the process of grouping visual elements together.  Perceptual Mechanism: Perceptual mechanism consists of three sub-processes, viz., selection, organization and interpretation.  Assessing Loyalty: Another important judgment that managers decide about employees is whether they are loyal to the organization.  Interpersonal Perception: Interpersonal perception is the process of making meaning from people and relationship interact with in our daily lives.  Perceptual Constancy: Perceptual constancy refers to the tendency to perceive an object you are familiar with as having a constant shape, size and brightness. 6.18 Learning Activity 1. You are required to prepare a live project on “Perception of Speech” with respect to psychology. _________________________________________________________________ _________________________________________________________________ 2. You are suggested to identify the types of perception and their link for experimental psychology. _________________________________________________________________ _________________________________________________________________ CU IDOL SELF LEARNING MATERIAL (SLM)

172 Experimental Psychology 6.19 Unit End Exercises (MCQs and Descriptive) A. Descriptive Type Questions 1. Discuss the concept of Perception. 2. Give the meaning of Perception. 3. Discuss the nature of Perception. 4. Explain in details about importance of Perception. 5. Discuss various types of Perception. 6. Explain various steps in Process of Perception. 7. Discuss various elements of Perception. 8. Write note on Perceptual Organization. 9. What is Perceptual Mechanism? 10. Discuss the perception and its application in organizations. B. Multiple Choice Questions 1. Which of the following is the process of attaining awareness or understanding of the environment by organizing and interpreting sensory information? (a) Perception (b) Communication (c) Presentation (d) Organizational Behavior 2. Who defined “Perception is the process by which an individual selects organizes and interprets stimuli into meaningful and coherent picture of the world”? (a) Schiffman and Kanuk (b) Mr. Fred Luthans (c) Joseph Reitz (d) Ajit Singh CU IDOL SELF LEARNING MATERIAL (SLM)

Perception 173 3. Perception is considered to be __________. (a) An intellectual process (b) A basic cognitive or psychological process (c) A subjective process and different people may perceive the same event differently (d) All the above 4. Which of the following is the type of Perception? (a) Perception of sound (b) Perception of speech (c) Perception of touch (d) All the above 5. Which of the following is not the element of Perception? (a) Sensation (b) Absolute Threshold (c) Subliminal Perception (d) Olfactory System Answers: 1. (a), 2. (a), 3. (d), 4. (d), 5. (d) 6.20 References References of this unit have been given at the end of the book.  CU IDOL SELF LEARNING MATERIAL (SLM)

174 Experimental Psychology UNIT 7 PSYCHOPHYSICS Structure: 7.0 Learning Objectives 7.1 Introduction 7.2 The Concept of Psychophysics 7.3 Gustav Fechner 7.4 Basic Concepts of Psychophysics 7.5 Classical Psychophysics 7.6 ProblemAreas of Interest to Classical Psychophysics 7.7 Methods of Classical Psychophysics 7.8 Summary 7.9 Key Words/Abbreviations 7.10 LearningActivity 7.11 Unit End Exercises (MCQs and Descriptive) 7.12 References 7.0 Learning Objectives After studying this unit, you will be able to:  Explain the basics of psychophysics  Discuss about classical psychophysics CU IDOL SELF LEARNING MATERIAL (SLM)

Psychophysics 175 7.1 Introduction Psychophysics is the scientific study of the relationship between stimuli specified in physical terms and the sensations and perceptions evoked by these stimuli. The term psychophysics is used to denote both the substantive study of stimulus-response relationships and the methodologies used for this study. Psychophysics deals with the nature of the quantitative relationship between physical and mental qualities. Today, the practice of psychophysics is ubiquitous in all fields of neuroscience that involve the study of behaving organisms, be they man or beast. 7.2 The Concept of Psychophysics Psychophysics originated with the research of Gustav Fechner (1801-1887), who first studied the relationship between incoming physical stimuli and the responses to them. Psychophysicists have generally used two approaches in studying our sensitivity to stimuli around us: measuring the absolute threshold or discovering the difference threshold. In studying the absolute threshold using the method of constant stimuli, an experimenter will, for example, produce an extremely faint tone which the listener cannot hear, then gradually increase the intensity until the person can just hear it; on the next trial, the experimenter will play a sound that is clearly heard, then reduce its intensity until the listener can no longer hear it. Thresholds can also be ascertained through the method of constant stimuli. In this approach, stimuli of varying intensity are randomly presented. Although an observer’s measured threshold will change depending on methodology, this technique gives an estimate of an individual's sensitivity. A different psychophysical approach combines the concept of sensory abilities with the decisions and strategies that an observer uses to maximize performance in a difficult task. Rather than try to identify a single point for the threshold, psychophysicists who employ the signal detection theory have developed ways to measure an observer’s sensitivity to stimuli in ways that go beyond the simple concept of the threshold. Some psychophysical research involves the identification of stimuli. CU IDOL SELF LEARNING MATERIAL (SLM)

176 Experimental Psychology There may be no question as to whether we can detect a stimulus, but sometimes we cannot identify it. For example, people can often detect odors but cannot identify them. Research in this area has centered on determining how much information is needed to allow a person to identify a stimulus. Identification constitutes a relatively small part of psychophysical research, although such research has important practical applications. For example, in the development of useful telephones, researchers had to assess how much “noise” or unwanted sound could accompany speech in a phone conversation so that a listener could understand what was said that is, identify the spoken words accurately. A third area of psychophysics involves discrimination of different stimuli, or difference thresholds. No two physical stimuli are absolutely identical, although they may seem to be. The question of interest here is how large must the difference be between two stimuli in order for us to detect it. The amount by which two stimuli must differ in order for us to detect the difference is referred to as the jnd, or just noticeable difference. Research has indicated that for stimuli of low intensity, we can detect a difference that is small, as the intensity increases, we need a larger difference. Sometimes, psychophysicists use reaction time as a measure of how different two stimuli are from one another. When two stimuli are very similar, it takes a longer time to decide if they are different, whereas large differences lead to fast reaction times. 7.3 Gustav Fechner Gustav Fechner, in full Gustav Theodor Fechner, (born April 19, 1801, Gross Särchen, near Muskau, Lusatia died November 18, 1887, Leipzig, Germany), German physicist and philosopher who was a key figure in the founding of psychophysics, the science concerned with quantitative relations between sensations and the stimuli producing them. CU IDOL SELF LEARNING MATERIAL (SLM)

Psychophysics 177 Fig. 7.1: Gustav Fechner Although he was educated in biological science, Fechner turned to mathematics and physics. In 1834 he was appointed Professor of Physics at the University of Leipzig. His health broke down several years later; his partial blindness and painful sensitivity to light in all likelihood developed as a result of his gazing at the Sun during the study of visual afterimages (1839-40). Pensioned modestly by the university in 1844, he began delving more deeply into philosophy and conceived of a highly animistic universe with God as its soul. He discussed his idea of a universal consciousness at length in a work containing his plan of psychophysics, Zend-Avesta: oder über die Dinge des Himmels und des Jenseits (1851; Zend-Avesta: On the Things of Heaven and the Hereafter). Fechner’s Elemente der Psychophysik, 2 vol. (1860; Elements of Psychophysics), established his lasting importance in psychology. In this work, he postulated that mind and body, though appearing to be separate entities, are actually different sides of one reality. He also developed experimental procedures, still useful in experimental psychology, for measuring sensations in relation to the physical magnitude of stimuli. Most important, he devised an equation to express the theory of the just- CU IDOL SELF LEARNING MATERIAL (SLM)

178 Experimental Psychology noticeable difference, advanced earlier by Ernst Heinrich Weber. This theory concerns the sensory ability to discriminate when two stimuli (e.g., two weights) are just noticeably different from each other. Later research has shown, however, that Fechner’s equation is applicable within the midrange of stimulus intensity and then holds only approximately true. Areas of Investigation by Gustav Fechner The experiments of psychophysicists concentrate on employing physical stimuli and relating them to sensation. These stimuli must be objectively measured; an example of this is the variation of lights in terms of luminance. Vision, hearing, taste, smell, touch and time have been constantly studied by psychophysicists. The areas of investigation involved in their experiments include thresholds (absolute or discrimination) and scaling. A threshold refers to the intensity point where the subject is able to detect a stimulus, whether the presence of such or the difference between stimuli. Another term used for threshold is “limen”, and stimuli that have below-threshold intensities and hence cannot be detected are called “sub-liminal”. The two types of threshold – absolute and discrimination – are considered as two different areas of investigation in psychophysics. Absolute threshold or detection threshold is an intensity level of the stimulus wherein a person can detect the presence of the stimulus in relation to some proportion of time (p). On the other hand, discrimination or difference threshold is the intensity of the smallest difference between stimuli that possess different intensities as detected by the participant at some proportion of time (p). To do this, the researcher may use several methods. The most often used method is asking the subject to perform adjustment/s to one of the stimuli until he perceives that it is at the same intensity level as the other stimulus. Scaling is a branch of measurement in which quantitative metric units are used to express qualitative constructs by means of creating a research instrument. Examples of scales used in psychophysics include Likert scale, Guttman scale and Thurston scale. CU IDOL SELF LEARNING MATERIAL (SLM)

Psychophysics 179 Thresholds of Psychophysics Psychophysicists usually employ experimental stimuli that can be objectively measured, such as pure tones varying in intensity, or lights varying in luminance. All the senses have been studied: vision, hearing, touch (including skin and enteric perception), taste, smell and the sense of time. Regardless of the sensory domain, there are three main areas of investigation: absolute thresholds, discrimination thresholds and scaling. A threshold (or limen) is the point of intensity at which the participant can just detect the presence of a stimulus (absolute threshold) or the presence of a difference between two stimuli (difference threshold). Stimuli with intensities below the threshold are considered not detectable (hence: sub-liminal). Stimuli at values close enough to a threshold will often be detectable some proportion of occasions; therefore, a threshold is considered to be the point at which a stimulus, or change in a stimulus, is detected some proportion p of occasions. Detection An absolute threshold is the level of intensity of a stimulus at which the subject is able to detect the presence of the stimulus some proportion of the time (a p level of 50% is often used). An example of an absolute threshold is the number of hairs on the back of one's hand that must be touched before it can be felt – a participant may be unable to feel a single hair being touched, but may be able to feel two or three as this exceeds the threshold. Absolute threshold is also often referred to as detection threshold. Several different methods are used for measuring absolute thresholds. Discrimination A difference threshold (or just noticeable difference, jnd) is the magnitude of the smallest difference between two stimuli of differing intensities that the participant is able to detect some proportion of the time (the percentage depending on the kind of task). To test this threshold, several different methods are used. The subject may be asked to adjust one stimulus until it is perceived as the same as the other (method of adjustment), may be asked to describe the direction and magnitude of the difference between two stimuli, or may be asked to decide whether intensities in a pair of stimuli are the same or not (forced choice). The just-noticeable difference (jnd) is not a fixed quantity; CU IDOL SELF LEARNING MATERIAL (SLM)

180 Experimental Psychology rather, it depends on how intense the stimuli being measured are and the particular sense being measured. Weber’s Law states that the just-noticeable difference of a stimulus is a constant proportion despite variation in intensity. In discrimination experiments, the experimenter seeks to determine at what point the difference between two stimuli, such as two weights or two sounds, is detectable. The subject is presented with one stimulus, for example a weight, and is asked to say whether another weight is heavier or lighter (in some experiments, the subject may also say the two weights are the same). At the point of subjective equality (PSE), the subject perceives the two weights to be the same. The just-noticeable difference, or difference limen (DL), is the magnitude of the difference in stimuli that the subject notices some proportion p of the time (50% is usually used for p in the comparison task). In addition, a two-alternative forced choice (2-afc) paradigm can be used to assess the point at which performance reduces to chance on a discrimination between two alternatives (p will then typically be 75% since p = 50% corresponds to chance in the 2-afc task). Absolute and difference thresholds are sometimes considered similar in principle because there is always background noise interfering with our ability to detect stimuli. 7.4 Basic Concepts of Psychophysics Psychophysics serves as a fusion of psychology and physics in which the physical stimuli and its properties relate to one’s sensory processes. Because of this, psychophysics may also refer to a category of classical methods that are used to analyze an organism’s perception. Basic concepts of Psychophysics are as follows: 1. Absolute threshold: As the stimulus strengthens from the undetectable, the point at which the person first detects it. 2. Signal detection theory: Theory pertaining to the interaction of the sensory capabilities and the decision makes factors in detecting a stimulus. 3. Difference thresholds: At which point can one differentiate between two stimuli. This point is termed just noticeable difference. 4. Scaling: Using rating scales to assign relative values (e.g., rating on a scale of one to ten) to sensory experiences. CU IDOL SELF LEARNING MATERIAL (SLM)

Psychophysics 181 The final area of interest to psychophysicists is scaling, the activity of deciding how large or small something is or how much of it is present. Any sensory experience can be scaled. For instance, if the attractiveness of a painting is rated on a scale of one to ten, it is being scaled. If the painting is rated nine, it is considered more attractive than a painting rated eight. This simple example gives the concept underlying scaling, but psychologists have developed more complicated techniques and sophisticated mathematical approaches to scaling. 7.5 Classical Psychophysics The classical psychophysics makes reference to a subdivision of the psychological field, in which the central subject is the relationship existing between the sensations experienced by an individual and the environmental stimuli that originate them. This subfield of study comes to represent a branch of psychology because it intends to explain and represent in a quantitative manner, how the internal process of perception is given. Psychologists still use the procedures developed by Fechner and they are still called psychophysical methods. But what is being measured is not the relationship between mind and matter. Sensation instead is considered as a hypothetical construct. We measure stimuli and certain types of behaviors that occur after the stimulus has been presented to the individual. To explain the consistency of various behaviors scientists have postulated the concept of sensation—an event that happens inside the animal. Sensation is a hypothetical construct, it is not an element of conscious experience which in the past was called sensation. The term “sensation” is now a technical term and does not have the meaning given to the word when it is used in everyday, non-technical conversations. This change in meaning is very important to remember. In testing we talk about the validity of a test to what extent does the test actually measure what we see it measures? There are several ways that we can go about actually measuring validity. One type of validity is that of face validity. All face validity does is ask, “Does this test convince the subject that it measures what it says it measures?” Some tests have unscored items that increase face validity but if those items were scores would make the test less valid. Many concepts in the basic areas of psychology are tricky for CU IDOL SELF LEARNING MATERIAL (SLM)

182 Experimental Psychology we use as a technical concept an everyday word. What we unconsciously do is try to use the word both ways at the same time. Sometimes, it is possible to do this and sometimes it is not possible. Sometimes, we can read the word “sensation” in the text and think of our conscious content—at that moment, for that context, the word “sensation” has face validity. Other times, the term “sensations” will be used and it cannot be referenced to your conscious content. In this second usage, the term does not have face validity. Nevertheless, in the second case, “sensation” may be a good hypothetical construct for it may be doing a fine job of integrating and predicting—and for science's criteria, that makes the term useful. 7.6 Problem Areas of Interest to Classical Psychophysics 1. Threshold determinations—liminal values of stimuli: What amounts of stimuli produce certain types of behavior. 2. Absolute Thresholds (RL): What is the weakest stimulus that will produce a sensation. Defining this stimulus presents several problems because the threshold seemingly varies from moment to moment. Consequently, there is no one single value for the RL. Instead there is a range of values. 3. In addition, we have a conceptual problem. If I flash a weak light one time you either see it or you do not see it. Let us say you do not see it. Now, let us flash that same light on 10 different trials. You might report seeing the light 8 of the 10 times. Is it above, below, or at threshold? In theory, no matter how weak a stimulus I present, if it is presented enough times, it will elicit a response on some occasion. Consequently, the usual definition of threshold takes into account the variability and defines the RL statistically—as for example, the stimulus which can be reported 50% of the time. But remember, the basic definition will always be the operational definition. In this case, the operational definitions are the psychophysical methods developed by Fechner. 4. Difference Thresholds (DL): What is the smallest difference between two stimuli which can be sensed. Again, the actual definition takes into account the statistical nature and variability of the threshold and defines the DL as that stimulus which is just noticeably CU IDOL SELF LEARNING MATERIAL (SLM)

Psychophysics 183 different from the standard stimulus 50% of the time. What is the DL at 100 gms (3.21 oz; approximately a quarter pound)? Here, 100 gm is the standard stimulus and using one of the psychophysical methods the DL is 103 gm, i.e., the stimulus that is just noticeably heavier. The difference between the standard stimulus and the difference limen is the just noticeable difference of the end, and in this case, it is 3 gm. 5. Scaling. These are interested in discovering the way in which sensations (or more operationally defined, the magnitude of our response) increase as the intensity of the stimulus increases. Generally we can say it is a monotonically increasing function (as stimulation becomes larger, our response never gets smaller) but that leaves the field wide open. 6. Psychometric Scaling, These are interested in scaling the sensations evoked by stimuli that I cannot measure physically in any meaningful way—meaningful here indicates that whatever measures I can take are not useful in determining factual meaning; the empirically determined relationship between two independently defined operational definitions. 7.7 Methods of Classical Psychophysics Classical psychophysical methods are as follows: Psychophysical experiments have traditionally used three methods for testing subjects' perception in stimulus detection and difference detection experiments: the method of limits, the method of constant stimuli and the method of adjustment. Method of Limits In the ascending method of limits, some property of the stimulus starts out at a level so low that the stimulus could not be detected, and then this level is gradually increased until the participant reports that they are aware of it. For example, if the experiment is testing the minimum amplitude of sound that can be detected, the sound begins too quietly to be perceived, and is made gradually louder. In the descending method of limits, this is reversed. In each case, the threshold is considered to be the level of the stimulus property at which the stimuli are just detected. CU IDOL SELF LEARNING MATERIAL (SLM)

184 Experimental Psychology In experiments, the ascending and descending methods are used alternately and the thresholds are averaged. A possible disadvantage of these methods is that the subject may become accustomed to reporting that they perceive a stimulus and may continue reporting the same way even beyond the threshold (the error of habituation). Conversely, the subject may also anticipate that the stimulus is about to become detectable or undetectable and may make a premature judgment (the error of anticipation). To avoid these potential pitfalls, Georg von Békésy introduced the staircase procedure in 1960 in his study of auditory perception. In this method, the sound starts out audible and gets quieter after each of the subject’s responses, until the subject does not report hearing it. At that point, the sound is made louder at each step, until the subject reports hearing it, at which point it is made quieter in steps again. This way the experimenter is able to “zero in” on the threshold. Method of Constant Stimuli Instead of being presented in ascending or descending order, in the method of constant stimuli the levels of a certain property of the stimulus are not related from one trial to the next, but presented randomly. This prevents the subject from being able to predict the level of the next stimulus, and therefore reduces errors of habituation and expectation. For ‘absolute thresholds’ again, the subject reports whether he or she is able to detect the stimulus. For ‘difference thresholds’, there has to be a constant comparison stimulus with each of the varied levels. Friedrich Hegelmaier described the method of constant stimuli in an 1852 paper. This method allows for full sampling of the psychometric function, but can result in a lot of trials when several conditions are interleaved. Method of Adjustment The method of adjustment asks the subject to control the level of the stimulus, instructs them to alter it until it is just barely detectable against the background noise, or is the same as the level of another stimulus. This is repeated many times. This is also called the method of average error. In this method, the observer himself controls the magnitude of the variable stimulus beginning with a variable that is distinctly greater or lesser than a standard one and he varies it until he is satisfied by the subjectivity of two. The difference between the variable stimuli and the standard one is recorded after each adjustment and the error is tabulated for a considerable series. At the end, mean is calculated giving the average error which can be taken as the measure of sensitivity. CU IDOL SELF LEARNING MATERIAL (SLM)

Psychophysics 185 Adaptive Psychophysical Methods The classic methods of experimentation are often argued to be inefficient. This is because, in advance of testing, the psychometric threshold is usually unknown and much data is collected at points on the psychometric function that provides little information about the parameter of interest, usually the threshold. Adaptive staircase procedures (or the classical method of adjustment) can be used such that the points sampled are clustered around the psychometric threshold. However, the cost of this efficiency is that there is less information regarding the psychometric function’s shape. Adaptive methods can be optimized for estimating the threshold only, or threshold and slope. Adaptive methods are classified into staircase procedures (see below) and Bayesian or maximum-likelihood methods. Staircase methods rely on the previous response only and are easier to implement. Bayesian methods take the whole set of previous stimulus-response pairs into account and are believed to be more robust against lapses in attention. Staircase Procedures Staircases usually begin with a high intensity stimulus, which is easy to detect. The intensity is then reduced until the observer makes a mistake, at which point the staircase ‘reverses’ and intensity is increased until the observer responds correctly, triggering another reversal. The values for the last of these ‘reversals’ are then averaged. There are many different types of staircase procedures, using different decision and termination rules. Step-size, up/down rules and the spread of the underlying psychometric function dictate where on the psychometric function they converge. Threshold values obtained from staircases can fluctuate wildly. So, care must be taken in their design. Many different staircase algorithms have been modeled and some practical recommendations suggested by Garcia- Perez. One of the more common staircase designs (with fixed-step sizes) is the 1-up-N-down staircase. If the participant makes the correct response N times in a row, the stimulus intensity is reduced by one step size. If the participant makes an incorrect response, the stimulus intensity is increased by the one size. A threshold is estimated from the mean midpoint of all runs. This estimate approaches, asymptotically, the correct threshold. CU IDOL SELF LEARNING MATERIAL (SLM)

186 Experimental Psychology Bayesian and Maximum-likelihood Procedures Bayesian and maximum-likelihood adaptive procedures behave, from the observer’s perspective, similar to the staircase procedures. The choice of the next intensity level works differently, however: After each observer response, from the set of this and all previous stimulus/response pairs the likelihood is calculated of where the threshold lies. The point of maximum likelihood is then chosen as the best estimate for the threshold, and the next stimulus is presented at that level (since a decision at that level will add the most information). In a Bayesian procedure, a prior likelihood is further included in the calculation. Compared to staircase procedures, Bayesian and ML procedures are more time-consuming to implement but are considered to be more robust. Well-known procedures of this kind are Quest, ML-PEST, and Kontsevich and Tyler’s method. Magnitude Estimation In the prototypical case, people are asked to assign numbers in proportion to the magnitude of the stimulus. This psychometric function of the geometric means of their numbers is often a power law with stable, replicable exponent. Although contexts can change the law and exponent, that change too is stable and replicable. Instead of numbers, other sensory or cognitive dimensions can be used to match a stimulus and the method then becomes “magnitude production” or “cross- modality matching”. The exponents of those dimensions found in numerical magnitude estimation predict the exponents found in magnitude production. Magnitude estimation generally finds lower exponents for the psychophysical function than multiple-category responses, because of the restricted range of the categorical anchors, such as those used by Likert as items in attitude scales. 7.8 Summary Psychophysics is the scientific study of the relationship between stimuli specified in physical terms and the sensations and perceptions evoked by these stimuli. The term psychophysics is used to denote both the substantive study of stimulus-response relationships and the methodologies used for this study. Psychophysics deals with the nature of the quantitative relationship between physical and mental qualities. Today, the practice of psychophysics is ubiquitous in all fields of neuroscience that involve the study of behaving organisms, be they man or beast. CU IDOL SELF LEARNING MATERIAL (SLM)

Psychophysics 187 Psychophysics originated with the research of Gustav Fechner (1801-1887), who first studied the relationship between incoming physical stimuli and the responses to them. Psychophysicists have generally used two approaches in studying our sensitivity to stimuli around us: measuring the absolute threshold or discovering the difference threshold. In studying the absolute threshold using the method of constant stimuli, an experimenter will, for example, produce an extremely faint tone which the listener cannot hear, then gradually increase the intensity until the person can just hear it; on the next trial, the experimenter will play a sound that is clearly heard, then reduce its intensity until the listener can no longer hear it. Thresholds can also be ascertained through the method of constant stimuli. In this approach, stimuli of varying intensity are randomly presented. Although an observer’s measured threshold will change depending on methodology, this technique gives an estimate of an individual’s sensitivity. Gustav Fechner, in full Gustav Theodor Fechner (born 19 April 1801, Gross Särchen, near Muskau, Lusatia died 18 November 1887, Leipzig, Germany), German physicist and philosopher who was a key figure in the founding of psychophysics, the science concerned with quantitative relations between sensations and the stimuli producing them. The experiments of psychophysicists concentrate on employing physical stimuli and relating them to sensation. These stimuli must be objectively measured; an example of this is the variation of lights in terms of luminance. Vision, hearing, taste, smell, touch and time have been constantly studied by psychophysicists. Psychophysicists usually employ experimental stimuli that can be objectively measured, such as pure tones varying in intensity, or lights varying in luminance. All the senses have been studied: vision, hearing, touch (including skin and enteric perception), taste, smell and the sense of time. Regardless of the sensory domain, there are three main areas of investigation: absolute thresholds, discrimination thresholds and scaling. An absolute threshold is the level of intensity of a stimulus at which the subject is able to detect the presence of the stimulus some proportion of the time (a p level of 50% is often used). An example of an absolute threshold is the number of hairs on the back of one’s hand that must be touched before it can be felt – a participant may be unable to feel a single hair being touched, but CU IDOL SELF LEARNING MATERIAL (SLM)

188 Experimental Psychology may be able to feel two or three as this exceeds the threshold. Absolute threshold is also often referred to as detection threshold. Several different methods are used for measuring absolute thresholds. Psychophysics serves as a fusion of psychology and physics in which the physical stimuli and its properties relate to one’s sensory processes. Because of this, psychophysics may also refer to a category of classical methods that are used to analyze an organism’s perception. The classical psychophysics makes reference to a subdivision of the psychological field, in which the central subject is the relationship existing between the sensations experienced by an individual and the environmental stimuli that originate them. This subfield of study comes to represent a branch of psychology because it intends to explain and represent in a quantitative manner, how the internal process of perception is given. Psychologists still use the procedures developed by Fechner and they are still called psychophysical methods. But what's being measured is not the relationship between mind and matter. Sensation instead is considered as a hypothetical construct. We measure stimuli and certain types of behaviors that occur after the stimulus has been presented to the individual. To explain the consistency of various behaviors scientists have postulated the concept of sensation—an event that happens inside the animal. Sensation is a hypothetical construct, it is not an element of conscious experience which in the past was called sensation. The term “sensation” is now a technical term and does not have the meaning given to the word when it is used in everyday, non-technical conversations. This change in meaning is very important to remember. There are several ways that we can go about actually measuring validity. One type of validity is that of face validity. Some tests have unscored items that increase face validity but if those items were scores would make the test less valid. Many concepts in the basic areas of psychology are tricky for we use as a technical concept an everyday word. Psychophysical experiments have traditionally used three methods for testing subjects’ perception in stimulus detection and difference detection experiments: the method of limits, the method of constant stimuli and the method of adjustment. CU IDOL SELF LEARNING MATERIAL (SLM)

Psychophysics 189 In the ascending method of limits, some property of the stimulus starts out at a level so low that the stimulus could not be detected, and then this level is gradually increased until the participant reports that they are aware of it. For example, if the experiment is testing the minimum amplitude of sound that can be detected, the sound begins too quietly to be perceived, and is made gradually louder. In the descending method of limits, this is reversed. In each case, the threshold is considered to be the level of the stimulus property at which the stimuli are just detected. In experiments, the ascending and descending methods are used alternately and the thresholds are averaged. A possible disadvantage of these methods is that the subject may become accustomed to reporting that they perceive a stimulus and may continue reporting the same way even beyond the threshold (the error of habituation). Conversely, the subject may also anticipate that the stimulus is about to become detectable or undetectable and may make a premature judgment (the error of anticipation). The method of adjustment asks the subject to control the level of the stimulus, instructs them to alter it until it is just barely detectable against the background noise, or is the same as the level of another stimulus. This is repeated many times. This is also called the method of average error. In this method, the observer himself controls the magnitude of the variable stimulus beginning with a variable that is distinctly greater or lesser than a standard one and he varies it until he is satisfied by the subjectivity of two. The difference between the variable stimuli and the standard one is recorded after each adjustment and the error is tabulated for a considerable series. At the end, mean is calculated giving the average error which can be taken as the measure of sensitivity. The classic methods of experimentation are often argued to be inefficient. This is because, in advance of testing, the psychometric threshold is usually unknown and much data is collected at points on the psychometric function that provides little information about the parameter of interest, usually the threshold. Adaptive staircase procedures (or the classical method of adjustment) can be used such that the points sampled are clustered around the psychometric threshold. However, the cost of this efficiency is that there is less information regarding the psychometric function’s shape. Adaptive methods can be optimized for estimating the threshold only, or threshold and slope. Adaptive methods are classified into staircase procedures (see below) and Bayesian or maximum-likelihood methods. Staircase methods rely on the previous response only and are easier to implement. Bayesian methods take the whole set of previous stimulus-response pairs into account and are believed to be CU IDOL SELF LEARNING MATERIAL (SLM)

190 Experimental Psychology more robust against lapses in attention. Staircases usually begin with a high intensity stimulus, which is easy to detect. The intensity is then reduced until the observer makes a mistake, at which point the staircase ‘reverses’ and intensity is increased until the observer responds correctly, triggering another reversal. The values for the last of these ‘reversals’ are then averaged. There are many different types of staircase procedures, using different decision and termination rules. Step-size, up/down rules and the spread of the underlying psychometric function dictate where on the psychometric function they converge. Threshold values obtained from staircases can fluctuate wildly. So, care must be taken in their design. Many different staircase algorithms have been modeled and some practical recommendations suggested by Garcia- Perez. Bayesian and maximum-likelihood adaptive procedures behave, from the observer’s perspective, similar to the staircase procedures. The choice of the next intensity level works differently, however: After each observer response, from the set of this and all previous stimulus/response pairs the likelihood is calculated of where the threshold lies. The point of maximum likelihood is then chosen as the best estimate for the threshold, and the next stimulus is presented at that level (since a decision at that level will add the most information). In a Bayesian procedure, a prior likelihood is further included in the calculation. 7.9 Key Words/Abbreviations  Psychophysics: Psychophysics is the scientific study of the relationship between stimuli specified in physical terms.  Gustav Fechner: Psychophysics originated with the research of Gustav Fechner.  Thresholds of Psychophysics: Thresholds can also be ascertained through the method of constant stimuli.  Detection: Absolute threshold is also often referred to as detection threshold.  Discrimination: Discrimination experiments, the experimenter seeks to determine at what point the difference between two stimuli. CU IDOL SELF LEARNING MATERIAL (SLM)

Psychophysics 191  Scaling: Using rating scales to assign relative values.  Classical Psychophysics: The classical psychophysics makes reference to a subdivision of the psychological field.  Sensation: Sensation instead is considered as a hypothetical construct.  Staircase Procedure: Staircases usually begin with a high intensity stimulus, which is easy to detect.  Magnitude Estimation: In the prototypical case, people are asked to assign numbers in proportion to the magnitude of the stimulus.  Difference Thresholds: DL as that stimulus which is just noticeably different from the standard stimulus 50% of the time.  Psychometric Scaling: These are interested in scaling the sensations evoked by stimuli that I cannot measure physically. 7.10 Learning Activity 1. You are required to prepare the project report on “Thresholds of Psychophysics”. _________________________________________________________________ _________________________________________________________________ 2. You are suggested to identify the methods of Classical Psychophysics. _________________________________________________________________ _________________________________________________________________ 7.11 Unit End Exercises (MCQs and Descriptive) A. Descriptive Type Questions 1. What is Psychophysics? 2. Discuss in details about concept of Psychophysics. CU IDOL SELF LEARNING MATERIAL (SLM)

192 Experimental Psychology 3. Explain the contribution of Gustav Fechner related to Psychophysics. 4. Discuss in details about Thresholds of Psychophysics. 5. What is Detection? Discuss in details about basic concepts of Psychophysics. 6. What is Scaling? Explain in details about Classical Psychophysics. 7. What is Sensation? Discuss in details about methods of Classical Psychophysics. B. Multiple Choice Questions 1. Which of the following is the scientific study of the relationship between stimuli specified in physical terms and the sensations and perceptions evoked by these stimuli? (a) Psychophysics (b) Psychological law (c) Sensory Processes (d) None of the above 2. The experiments of psychophysicists concentrate on employing physical stimuli and relating them to __________. (a) Sensation (b) Stimuli (c) Vision (d) Taste 3. Which of the following is the basic concept of Psychophysics? (a) Absolute threshold – As the stimulus strengthens from the undetectable, the point at which the person first detects it. (b) Signal detection theory – Theory pertaining to the interaction of the sensory capabilities and the decision makes factors in detecting a stimulus. (c) Scaling – Using rating scales to assign relative values (for example, rating on a scale of one to ten) to sensory experiences. (d) All the above CU IDOL SELF LEARNING MATERIAL (SLM)

Psychophysics 193 4. Psychologists still use the procedures developed by Fechner and they are still called __________. (a) Complexity methods (b) Psychophysical methods (c) Perception (d) None of the above 5. Which of the following is not the method of Classical Psychophysics? (a) Method of Limits (b) Method of Adjustment (c) Adaptive Psychophysical Methods (d) Method of Discrimination Answers: 1. (a), 2. (a), 3. (d), 4. (b), 5. (d) 7.12 References References of this unit have been given at the end of the book.  CU IDOL SELF LEARNING MATERIAL (SLM)

194 Experimental Psychology UNIT 8 SIGNAL DETECTION THEORY Structure: 8.0 Learning Objectives 8.1 Introduction 8.2 Signal Detection Theory 8.3 Basic Concept of Signal Detection Theory 8.4 Assumptions of Signal Detection Theory 8.5 Applications of Signal Detection Theory 8.6 Summary 8.7 Key Words/Abbreviations 8.8 LearningActivity 8.9 Unit End Exercises (MCQs and Descriptive) 8.10 References 8.0 Learning Objectives After studying this unit, you will be able to:  Explain the applicability of signal detection theory  Discuss about basic concept of signal detection theory CU IDOL SELF LEARNING MATERIAL (SLM)