Chapter 6: Perceiving the World

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CHAPTER 6: PERCEIVING THE WORLD

I. Murder!

1. Perceptual Constancies

1. Perception – mental process of organizing sensations into meaningful patterns.

B. Process – energy patterns reaching our senses are constantly changing; however, perceptual constancies rescue us from a confusing world in which objects would seem to shrink and g row and change shape as if made of rubber or fade.

1. size constancy – the perceived size of an object remains constant, despite changes in its retinal image.
2. native perception – a perceptual experience based on innate processes; appear to be innate (born) such as the ability to see a line on a paper.
3. empirical perception – perception strongly influenced by prior expectation. Ex: pygmy from dense forest to plains.
4. shape constancy – the perceived shape of an object is unaffected by changes in its retinal image.
5. brightness constancy – the apparent/relative brightness of objects remains the same as long as they are illuminated by the same amount of light.

1. Perceptual Organization (role of learning)

1. Vocabulary

1. figure-ground organization – part of a stimulus appears to stand out as an object (figure) against a less prominent background (ground).
2. reversible figure – a stimulus pattern in which figure-ground organization can be reversed.
3. camouflage – designs that break up figure-ground organization.
4. perceptual hypothesis – an initial guess regarding how to organize or perceive/comprehend a stimulus pattern.

1. Gestalt Principles – how do we separate a figure from its background?

1. nearness
2. similarity
3. continuation, or continuity
4. closure – can create illusory figures: implied shape that is not actually bounded by an edge or an outline.
5. contiguity (nearness in time and space
6. common region

1. Engineering psychology (human factors engineering) – specialty concerned with making machines/work environments compatible with human perceptual and physical capacities.

1. Depth Perception

1. Vocabulary

1. depth perception – the ability to see three-dimensional space and to accurately judge distances; considered both learned (~4 moths) and innate.
2. visual cliff – an apparatus that looks like the edge of an elevated platform or cliff.
3. depth cues – perceptual features that impart information about distance and 3-dimensional space; features of the environment and messages from the body that supply information about distance and space; some cues will work with just one eye (monocular cues) and others require two eyes (binocular cues).

1. Muscular Cues – comes from the body.

1. accommodation – changes in the shape of the lens of the eye; bending of the lens to focus on nearby objects; monocular cue.
2. convergence – simultaneous turning inward of the two eyes; i.e., catching a fly ball.

1. Stereoscopic Vision – perception of space and depth caused chiefly by the fact that the eyes receive different images.

1. retinal disparity – small discrepancies in images on the right and left retinas; most basic source of depth perception; fuses two images into one and 3-deminsonal sight occurs.

V. Pictorial Cues for Depth – features found in paintings, drawings, and photographs that impart information about space, depth, and distance.

1. How is the illusion of depth created on a 2-dimensonal surface?

1. linear perspective – convergence implies great distance.
2. relative size – makes identical object smaller
3. height in the picture plane – objects that are placed higher tend to be perceived as more distant.
4. light and shadow - gives 3-dimensional appearance.
5. overlap/interposition – when one object partially blocks another object.
6. texture gradients – changes in texture can create sense of distance.
7. aerial perspective – smog, fog, dust, etc., add to apparent distance of an object.
8. relative motion/motion parallax – looking out a window and moving your head from side to side.

1. Moon Illusion – apparent change in size that occurs as the moon moves from horizon (large) to overhead (small); apparent distance hypothesis: an explanation of the moon illusion stating that the horizon seems more distant than the night sky because there are more depth cues present.

1. Perceptual Learning – changes in perception that can be attributed to prior experience.

1. Perceptual Habits – well established patterns of perceptual organization and attention.

1. perceptual features – important elements of a stimulus pattern, such as lines, shapes, edges, spots, and colors.
2. other-race-effect – the tendency to be better at recognizing faces from one’s own racial group than faces from other racial or ethnic groups.
3. active movement – self-generated action (a factor that accelerates perceptual adaptation).

1. Adaptation level

1. context – information surrounding a stimulus (environment).
2. frame of reference – an internal perspective relative to which events are perceived and evaluated.
3. adaptation level – an internal or mental “average” or “medium” point is used to judge amounts.

1. Illusions – a misleading or distorted perception; p. 232, Fig.6.27

1. hallucination – an imaginary sensation—such as seeing, hearing, or smelling something that does not exist in the external world.
2. stroboscopic movement – illusion of movement in which an object is shown in rapidly changing series of positions.
3. Muller-Lyer illusion – two equal-length lines tipped with inward or outward pointing V’s appear to be of different lengths.
4. size-distance invariance – the strict relationship between the distance an object lies from the eyes and the size of its image.

1. Motives and Perception

1. Attention

1. selective attention – giving priority to a particular incoming sensory message.
2. divided attention – allotting mental space or effort to various tasks or parts of a task.
3. automatic vs. controlled processing

1. Attention and perception

1. inattentional blindness – failure to perceive a stimulus that is in plain view, but not the focus of attention (occurs when person’s attention is directed elsewhere.)

1. Habituation – a decrease in perceptual response to a repeated stimulus.

1. orientation response – bodily changes that prepare an organism to receive information from a particular stimulus; i.e., “double-take.”

1. Motives – plays a role in attention; hunger, sex; men who read a sexually arousing passage found women more attractive.

1. Perceptual Expectancies

1. Vocabulary

1. bottom-up processing – organizing perceptions by beginning with low-level features, with small sensory units and build upward to a complex perception.
2. top-down processing – applying higher level knowledge to rapidly organize sensory information into a meaningful perception; use of preexisting knowledge is used to rapidly organize features into a meaningful whole.
3. perceptual set/expectancy – a readiness to perceive in a particular manner, induced by strong expectations; often lead us to see what we expected to see.
4. perceptual categories – a preexisting class, type, or groupings; based on learning; plays a role in how we perceive people.

1. Eyewitness – Factors affecting the accuracy of eyewitness perceptions p. 241; psychologists are gradually convincing lawyers, judges, and police that eyewitness errors are common. Weapon focus (tendency of crime victims to fix their attention on an attacker’s weapon). Sources: wording of questions; post event information, attitudes, expectations; alcohol intoxication; cross-racial perceptions; weapon focus; accuracy-confidence; exposure time; unconscious transference; color perception; and stress.

IX. Extrasensory Perception: ability to perceive events in ways that cannot be explained by know capacities of the sensory organs, i.e., perception without sensation. Most of the findings in parapsychology cannot be replicated.