1

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.