Sensation & Perception Lecture Notes PDF

Sensation and Perception  Sensation and Perception Sensation: The detection of physical energy emitted or reflected by physical objects; it occurs when energy in the external environment or the body stimulates receptors in the sense organs. Perception: The process by which individuals...

Sensation and Perception  Sensation and Perception Sensation: The detection of physical energy emitted or reflected by physical objects; it occurs when energy in the external environment or the body stimulates receptors in the sense organs. Perception: The process by which individuals organize and interpret sensory information in order to give meaning to their environment.  MEANING….. Perceptions differ from person to person. Each individual perceives the same situation differently. Group perceptions can influence and individual’s perception. Individuals organize and interpret things based on their past experiences and the important values they consider important.  Video (with notes) Sensation V Perception https://www.youtube.com/watch?v=feT1OdI6Htg Sensation  Psychophysics Psychophysics Psychophysics is the branch of psychology that studies the effects of physical stimuli on sensory perceptions and mental states. The field of psychophysics was founded by the German psychologist Gustav Fechner (1801–1887), who was the first to study the relationship between the strength of a stimulus and a person’s ability to detect the stimulus. The Absolute threshold of sensation: The smallest amount of the stimulus we can detect The difference threshold (or just noticeable difference [JND]), refers to the change in a stimulus that can just barely be detected by the organism. The German physiologist Ernst Weber (1795– 1878) made an important discovery about the JND—namely, that the ability to detect differences depends not so much on the size of the difference but on the size of the difference in relationship to the absolute size of the stimulus. Weber’s law maintains that the just noticeable difference of a stimulus is a constant proportion of the original intensity of the stimulus https://www.youtube.com/watch?v=-1e0uIS5j2Q (Weber’s Law)  Absolute Threshold (we can accurately report on its existence (or its nonexistence) better than 50% of the time) The human eye can detect the equivalent of a single candle flame burning 30 miles away and can distinguish among more than 300,000 different colors. The ear can detect sounds as low as 20 hertz (vibrations per second) and as high as 20,000 hertz, and it can hear the tick of a clock about 20 feet away in a quiet room. We can taste a teaspoon of sugar dissolved in 2 gallons of water, and we are able to smell one drop of perfume diffused in a three-room apartment. We can feel the wing of a bee on our cheek dropped from 1 centimeter above (Galanter, 1962).  Transduction is the conversion of stimuli detected by receptor cells to electrical impulses that are transported to the brain. Coding is when the brain converts particular stimuli into specific sensations To Summarize …. Perception  Perception The study of perception deals with the question of how organisms process and organize incoming raw sensory information in order to (1) form a coherent representation or model of the world within which the organism dwells and (2) use that representation to solve naturally occurring problems, such as navigating, grasping, and planning.  Perception Minute 4:11 – 6:30 https://www.youtube.com/watch?v=9tWUUBkNkfQ The distal stimulus is the external object which is sensed. proximal stimulus. Is representation of that distal stimulus on the sensory apparatus (e.g. retina) Functions of Perception  Five functions of perception Five major functions of the perceptual system are: (1) Attention: determining which part of the sensory environment to attend to, (2) Localization: or determining where objects are, (3) Recognizing, or determining what objects are, (4) Abstracting the critical information from objects, and (5) Perceptual constancy keeping the appearance of objects constant, even though their retinal images are changing. Another area of study is how our perceptual capacities develop.  1. Attention We have three anatomically distinct sets of processes in our brain enabling us to selectively attend to only a small part of all the information around us, one: is responsible for keeping us alert, is responsible for focussing on task relevant information only and decides whether we want to continue attending to the information or switch our attention to other information.  2. Localisation To localize objects, we must first separate them and then organize them into groups. Localization involves determining an object’s position in the up–down and left–right dimensions. This is relatively easy because the required information is part of our retinal image. Localizing an object also requires that we know its distance from us. This form of perception, known as depth perception, is not so easy because it’ not available in the retinal image. We have a variety of depth cues, both monocular and binocular, that allow us to do this. Localizing an object sometimes requires that we know the direction in which an object is moving.  Perceptual Groupings The Gestalt Laws of Perceptual Grouping. Objects in a scene appear to group pre-attentively according to certain laws or principles and based on distinctive features or their mutual positions https://www.youtube.com/watch?v=RWJSC1HU32c Some factors underlying grouping are: Continuity Closure Proximity Similarity A. Continuity/connectedness B. Proximity C. Similarity D. CLOSURE  E. Figure Ground Distinction (Determining where objects are) In order to localize objects, we have to separate them from their surrounding background. Usually, large things are perceived as the background of small things  IN GROUPS DRAW EXAMPLES OF PERCEPTUAL GROUPINGS EXAMPLE More elaborate examples Gestalt’s principles of perceptual groupings  3. Recognition (Determining what kind of object it is) Recognizing an object requires that the various features associated with the object (such as shapes and colors) be correctly bound together, a process that requires attention. Recognition of a particular object is aided by first acquiring ‘global’ aspects of the scene; for example quickly understanding that you are looking at a kitchen helps recognizing an ambiguous object as a loaf of bread rather than a mailbox.  3. Recognition cont. (Determining what kind of object it is) Recognizing an object entails binding together various features of an object such as its shape and its color. The features themselves are acquired via pre-attentive processes, while ‘gluing’ them together require attention.  4. Abstraction (critical features) Abstraction is the process of converting the raw sensory information acquired by the sense organs (for example, patterns of straight and curved lines) into abstract categories that are pre-stored in memory (for example letters or words). Abstracted information takes less space and is therefore faster to work with than raw information. A useful analogy is between a bitmapped computer image of a face versus an abstracted image of the same face that is made up of preformed structures such as ovals and lines. Advantages of Abstraction: Takes less space Faster to work with (e.g faster processing of images) Retention of the critical information Figure 5.23 Verbal Labels and Abstraction. Carmichael, Hogan, and Walter (1932) showed people the kind of ambiguous stimuli shown in the middle panel. Observers were given one of the two verbal labels shown in the second and fourth columns. The subjects’ later reconstructions of what they had seen conformed to the verbal label, as shown in the first and fifth columns. This experiment indicates that subjects remember not what they literally saw but rather abstract the fundamental information from it.  5. Perceptual constancy, Constancy- brain’s ability to maintain a perception of the underlying physical characteristics of an object, such as shape, size or colour, even when the sensory manifestations of these objects change drastically. https://study.com/academy/lesson/perceptual-constancy-in-psychology-definition-examples.html  Perceptual constancy Another major function of the perceptual system is to achieve perceptual constancy – to keep the appearance of objects the same in spite of large variations in the initial representations of the stimuli received by the sense organs that are engendered by various environmental factors. Color and brightness constancy entail perceiving the actual color and brightness of a stimulus even when the actual information arriving at the eye varies in color makeup (because of the color makeup of the ambient lighting) and in brightness (because of the level of ambient illumination)  Perceptual constancy Size constancy entails perceiving the actual size of a stimulus even when the actual size of the object’s image on the retina varies because of the object’s distance. Intrinsically, constancies entail ‘illusion’ in the sense that by a constancy’s very nature, perception differs systematically from the physical nature of the stimulus. It logically follows, and is empirically true that many visual illusions may be explained by the various constancies. Constancies occur in all sensory modalities. Various kinds of perceptual illusions can be explained by the perceptual system’s insistence on maintaining constancies. Although visual constancies are the most salient, constancies exist in all sensory modalities. Lecture 10 & 11 Learning and Conditioning  In Today’s Class We will discuss Classical Conditioning Next class we will discuss Operant Conditioning Observational Learning  Learning & Conditioning ‘Learning is defined as a relatively permanent change in behaviour that occurs due to experience’ Classical Conditioning  Classical Conditioning Classical conditioning Learning process in which previously neutral stimulus becomes associated with another stimulus through repeated pairing with that stimulus https://www.youtube.com/watch?v=jd7Jdug5S Rc (only to min 2:44) Classical Conditioning Pavlov’s experiments (1890s) Unconditioned stimulus (US) – food Unconditioned response (UR) – salivation Neutral stimulus (NS) – unrelated event, e.g. light on During conditioning, pair presentation of food with light After number pairings, dog will salivate when light is on Conditioned stimulus (CS) – light Conditioned response (CR) – salivation Classical Conditioning  exercise In groups of 3 Teach a cat to lick its lips at the sight of a book IMPLICATION OF THE ABOVE IN GROUP of 3 In groups of 3 can the above explain any If so how can we use the psychological problems above to treat these problems  Classical Conditioning Extinction – CR gradually diminishes if US omitted https://www.youtube.com/watch?v=hhqumfpxuzI 2.55mins Stimulus generalisation – tendency for stimuli similar to a CS to also elicit a CR Stimulus discrimination tendency for stimuli similar to a CS to stop eliciting a CR when they are not followed by a UCS.  Stimulus generalization circle to an ellipse  ‘Generalization’ The little albert experiment by Watson and Rayner (1920) https://www.youtube.com/watch?v=FMnhyGozLyE Stimulus Discrimination Shenger- Krestovnika (1921)  Classical Conditioning Higher-order conditioning – possible to condition participant to produce CR to novel stimulus by pairing novel stimulus to CS repeatedly even though novel stimulus never paired with US https://www.youtube.com/watch?v=zIBxmVIEV6E Operant/Instrumental Conditioning https://www.youtube.com/watch?v=H6LEcM0E0io  Operant/Instrumental Conditioning Instrumental conditioning Involves learning the relationship between responses and their outcomes Thorndike carried out experiments where animals engaged in trial-and-error learning where behavior strengthened if immediately followed by reward (law of effect) Instrumental conditioning (Thorndike)  Instrumental Conditioning Skinner’s experiments Skinner’s experiments involved putting a hungry animal in box which is bare except for a bar with food dish under. Acquisition & extinction – each time the bar is pressed food is released which results in frequent pressing of the bar. If food stops being released then similar extinction of response, as in classical conditioning.  Instrumental Conditioning https://www.youtube.com/watch?v=ne6o-uPJarA  Instrumental Conditioning Skinner’s experiments Shaping Conditioning by reinforcing only variations in behavior which deviate in the desired direction  Instrumental Conditioning Skinner’s experiments Schedules of reinforcement https://www.youtube.com/watch?v=I_ctJqjlrHA Ratio schedules – reinforcement depends on the number of responses an organism makes Interval schedules – reinforcement is available only after certain time interval elapsed (& animal makes a response) Operant conditioning (Skinner)  Learning and Cognition Observational learning Humans often learn without behavior being reinforced immediately through observational learning – copying behavior of others Bandura Models inform us about consequences of behavior – so reinforcement is “vicarious” Learner pay attention to a model’s behavior, remember & be able to reproduce behavior & be motivated to do so Observational learning SOCIAL PSYCHOLOGY  TODAY We will discuss… Definition of social psychology Bystander effect Compliance and Obedience Conformity Stereotype Threat Hopefully you will be able to Define social psychology Distinguish between key social psychology studies Describe Asche and Milgram’s study Detail what happened to Kitty Genovese and why this is important  SOCIAL PSYCHOLOGY Scientific study of ways in which people’s behavior & mental processes are shaped by the real (or imagined) presence of others How you behave and act when others are around (or you think others are around) and watching you  THE PRESENCE OF OTHERS Social facilitation Social Inhibition Deindividuation Bystander effect  SOCIAL FACILITATION & SOCIAL INHIBITION Social facilitation – presence of others improves performance on simple tasks Social inhibition – presence of others impairs performance on complex tasks  DEINDIVIDUATION Certain group situations minimize people’s personal identities & sense of accountability leading to aggressive/unusual behavior with anonymity & group size contributing factors  EXAMPLE You usually don’t cheat in exams You find out that lots of others cheating in exams You start cheating as well so that you don’t get singled out as a teacher’s pet BYSTANDER EFFECTS  BYSTANDER EFFECTS Refers to findings that people are less likely to help if others are present Possible Explanations: Pluralistic ignorance – where everybody in group misleads everybody else by defining situation as non-emergency (i.e. seeing no one else act, so it must not be an emergency (Las Vegas)* Diffusion of responsibility - Presence of others, even imagined others, diffuses responsibility so no one person feels need to act  THERE WAS THIS ONE TIME! Kitty Genovese Murdered in New York Screamed for help 35-45 people heard or saw the murder No one called for help https://www.youtube.com/watch?v=z4S1LLrSzVE  THE PRESENCE OF OTHERS BYSTANDER EFFECTS Research suggests if pluralistic ignorance & diffusion of responsibility minimised – people will help  CONFORMITY & OBEDIENCE: TO A MAJORITY Asch’s studies on conformity Suggest that unanimous agreement among a group exerts strong pressures on individual to conform, even when judgements clearly wrong If even one of the group disagrees, pressure to conform persists https://www.youtube.com/watch?v=qA-gbpt7Ts8  Milgram’s Study on Obedience https://www.youtube.com/watch?v=yr5cjyokVUs  COMPLIANCE & OBEDIENCE OBEDIENCE TO AUTHORITY Milgram’s studies on obedience to authority Showed that ordinary people would obey experimenter’s order to deliver strong electric shocks to innocent victim  COMPLIANCE & OBEDIENCE TO AUTHORITY Four important situational features in Milgram’s studies: 1. Surveillance: Constant presence of experimenter – increased obedience 2. Buffers: The more direct the participants’ interacts with the victim the less the participant will obey (Think about your friend versus someone you just met) 3. Role models: If role model disobeyed, participant chose conformity to disobey rather than obedience 4. Emerging situations: obedience dependent on harmless start to study, small rate of change in shock intensity & lack of time for reflection by participant  REFERENCE GROUPS & IDENTIFICATION Identification – process by which we obey group norms & adopt their beliefs, attitudes & behaviors in order to identify with the group Use reference groups (groups to identify with) to evaluate & regulate our opinions & actions Reference groups can also provide frame of reference from which to view world Do not have to be member of group to be influenced by its values  INTERNALIZATION From identification to internalization One advantage of internalisation over compliance is: changes are self-sustaining so test of internalization is long- term stability of induced beliefs, attitudes & behaviors When you internalize it becomes who you are, when you identify, it might be temporary  GROUP INTERACTIONS INSTITUTIONAL NORMS Like social norms (implicit or explicit rules for acceptable behavior & beliefs) but applied to entire institutions or organizations of same type (e.g. schools) Institutional norms strongly influence behavior Stanford prison experiment – participants randomly assigned “prisoner” or “guard” in simulated prison – vivid demonstration of the power of situations https://www.youtube.com/watch?v=oAX9b7agT9o Min 2-5:30 Watch on your own *  GROUP INTERACTIONS GROUP DECISION MAKING Groupthink Phenomenon in which group members suppress own dissent (avoid disagreement) in interests of group consensus Caused by: lack of outside influences; with no systematic procedures for considering pros & cons of action; a directive leader Consequences include: shared illusions of invulnerability, morality & unanimity; direct pressure on dissenters; etc.