Sensation and Perception

1. Sensation and Perception The Biological Basis of Behavior: Unit III

2. Bell Ringer 10.28.13 • Which perceptual cues (depth perception) are at use in this picture?

3. II. Perception • Understanding and interpreting sensations from a stimulus. Don't read the words -just say the colors they're printed in, and do this aloud as fast as you can.

5. III. Principles of Perception • 1. Stroop Effect • Preattentive process acts as an interference. • Recognizing and naming colors requires more of our attention than reading.

6. What do you see?

7. Perceptual Organization • 2. Gestalt Approach • Tendency to integrate pieces of information into meaningful wholes • We see patterns and groupings, instead of small, individual pieces.

8. Gestalt--”form/shape” • What is it? • Figure-ground relationship • How far away is it? • Depth Perceptions • Where is it going? • Perceptual constancies

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10. Depth Perceptoins

11. Gestalt examples • Proximity-when objects are close to one another we perceive them together rather than separately. • Similarity-people think of similar objects as belonging together. • Closure-to perceive a complete or whole figure even when there are gaps. • Continuity-people usually prefer to see smooth, continuous patterns. • Common Fate- objects moving in same direction belong together.

13. What do you see?

14. 3. Figure-Ground Perception • Organization of the visual field into objects (figures) that stand out from their surroundings (ground) • Perception of figures against a background.

17. Perception of motion • To sense movement, humans need to see an object change its position relative to other objects. • Traffic light • Stroboscopic motion • Produced by showing the rapid progression of images or objects that are not moving at all. • Flip books & movies

18. 4. perceptual set - predisposition to perceive something in relation to prior perceptual experiences • Interpretation of ambiguous stimuli • Face on Mars • UFOs • Nessie • Bigfoot

20. Old Lady or Young Woman?

22. Perceptual Constancies • Size constancy-an object is the same size no matter how far away it is or if its angle changes • Color constancy-objects keep their color though the light may change the appearance • Brightness constancy-object is equally bright though light changes • Shape constancy-object has only one shape no matter what angle you view it from

24. 5. optical illusions • SOMETIMES OUR VISUAL PECEPTION TRICKS US!

25. IMPOSSIBLE FIGURE This optical illusion works because we try to assign a three dimensional aspect to a two dimensional picture. The technique of perspective angles has been used.

27. Do you see grey dots? Explanation: The eye, which responds to an amazingly wide variety of light sources from moon light to direct sunlight, tries to adjust to the present light levels. In this optical illusion, the contrast between the black and white is so strong and irregular that the white ends up looking gray.

28. Which line is longer? Muller-Lyer illusion

29. Which box has the smaller man? Ponzo Illusion The tunnel creates a believable sense of perspective in this optical illusion. The second man looks bigger than it is because it seems to fill up the tunnel.

32. Are the lines below straight or are they curved?

33. IV. Depth Perception • A. The ability to see objects in three dimensions although the images that strike the retina are two dimensional. • B. We use perceptual cues to determine distance and depth

34. Perceptual Cues • 1. Interposition - If something is blocking our view, we perceive it as closer

36. 2. Relative Size - if we know that two objects are similar in size, the one that looks smaller is farther away (size constancy) • 3. Relative Height - things higher in our field of vision look farther away • 4. Linear Perspective - Parallel lines seem to converge with distance

38. Relative height & size

39. 5. Relative brightness – brighter objects appear closer than dimmer objects.

40. 6. aerial perspective – Atmospheric conditions (haze, dust) . Clearer objects seem closer.

42. Relative size • Linear perspective • Aerial perspective • Relative height • Interposition

44. V. Perception: Nature or Nurture • A. We learn to perceive … • *infants under I month will smile at a nodding object the size of a face, even if it has no features. After 20 weeks a blank oval will not make most infants smile. By 30 weeks infants will more likely smile if they see a familiar face.

45. B. We are born with the ability to perceive … • *The Visual Cliff Experiment