Chapter 6: Sensation and Perception

1. Chapter 6: Sensation and Perception

2. Upstate Some Definitions: • Sensation - process used by sense receptors to receive and store information from environment • Perception - process of organizing and interpreting sensory information allowing us to make sense of and recognize objects.

3. Upstate • Perceptual psychologists - often study illusions • Illusions – misperceptions; when we get it wrong, when we misperceive • Ex. - lines • This is also on page 240 in textbook • Which line is longer A - B or B - C?

4. Upstate Look at the following. What do you see?

5. Upstate • Gestalt psychologists studied perceptual organization • Gestalt - German word for “form” or “whole” • Gestalt psychologists - “the whole may differ from the sum of its parts” • Some Gestalt principles.

6. Upstate Gestalt Principles of Organization: • Figure-ground effect

7. Upstate Gestalt Principles of Grouping: Proximity Closure Continuity Similarity

8. Upstate Depth Perception • Depth Perception - the ability to see objects in three dimensions, although, the image that strikes the retina is two dimensional • Allows us to judge distance, to see some objects as close and other objects as far away.

9. Upstate • Gibson and Walk - depth perception and young children • Is depth perception innate? • 6 to 14 month old infants • Designed a visual cliff • Placed infants on the visual cliff - observed behavior.

10. Upstate Visual Cliff

11. Upstate • Findings - depth perception may be partly innate • Infants would not crawl out on the glass to get to their mother - perceived the drop off • But, by six to fourteen months … • Perhaps depth perception is due to experience. • Yet, newborn animals (kittens, chicks) would not walk on the glass area

12. Upstate • How do we perceive depth and distance from a two dimensional retinal image? • We have depth cues • Depth cues - binocular and monocular.

13. Upstate Binocular Cues • Depth and distance cues - depend on the use of two eyes • Retinal disparity - each eye perceives a slightly different world because … • We usually do not realize this. Yet, this fact provides an important cue to depth and distance.

14. Upstate • An Example • Retinal disparity is built into the viewmaster • How? • You are seeing two pictures - one in your right eye, the other in your left • What is the difference between pictures? • Convergence - the extent to which the eyes converge inward when looking at an object.

15. Upstate Monocular Cues • Cues to depth and distance available to either eye alone • First, some information . . . • Some examples . . .

16. Upstate Relative Size If we assume that two objects are similar in size, we perceive the one that casts a smaller retinal image as farther away. (p.246)

17. Upstate Relative Clarity Because light from distant objects passes through more atmosphere we perceive hazy objects as farther away than clear objects (effect of fog on judging distance). (p. 247)

18. Upstate Interposition If one object partially blocks the view of another we perceive it as closer. (p. 246)

19. Upstate Texture Gradient Relative Height A gradual change from a coarse, distinct texture to a fine indistinct texture signals increasing distance. (p. 247) Perceives objects higher in our field as farther away. (p. 247)

20. Upstate • Parallel lines, such as railroad tracks and cabbage rows, appear to converge with distance. (p.248) • The more the lines converge the greater their perceived distance. Linear Perspective

21. Upstate Perceptual Constancy • Perceptual Constancy - perceiving objects as unchanging, even though retinal images change • Ex. - size constancy • It’s fortunate that our retina does not talk and have decision-making ability. Why?

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23. Upstate Shape and Size Constancy

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25. Upstate The size/distance relationship is often related to misperception.

26. Upstate Another Example . . .

27. Upstate Perceptual Interpretation • Sensory Deprivation and Restored Vision • Born blind, operation corrects vision in adulthood • Can person see normally? • Cataracts removed… • distinguish figure from ground, but could not learn to recognize by sight objects that were familiar by touch • Critical period.

28. Upstate • Perceptual Adaptation. • Can we adapt to an artificially displaced or inverted visual field? • When subjects wear glasses that shift the apparent location of object 40 degrees to the left, can they adapt? • Yes, within a few minutes and with practice • experience brief aftereffect.

29. Upstate • If you wore goggles which completely inverted your perception, could you adapt and respond normally? • If you wore goggles which completely inverted your perception, could you adapt and respond normally? • After a period of adjustment, people wearing the inverted goggles have been able to ride a motorcycle, ski, and fly an airplane.

30. Upstate • Perceptual Set and Context Effects • This is a mental predisposition to perceive one thing and not another.

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35. Upstate Extrasensory Perception (ESP) • The controversial claim that perception can occur apart from sensory input.