1. Sensation and Perception

2. Sense: Translates outside information nervous system activity –“Sensations” Perception: Process that turns sensations into experience. Rotating Snakes Mach Bands

3. Figure 3.2: Elements of a Sensory System

4. Psychophysics

5. Absolute Thresholds: (minimum detectable stimulus) Difference Thresholds (Minimum detectable difference between two stimuli)

6. Some “Ideal” Absolute Thresholds Vision: A candle flame seen at 30 miles on a clear night (A single photon of light). Hearing: The tick of a watch under quiet conditions at 20 feet. Taste: One teaspoon of sugar in two gallons of water. Smell: One drop of perfume diffused into the entire volume of air in a six-room apartment. Touch: The wing of a fly falling on your cheek from a distance of one centimeter. Galanter, Eugene. 1962, Contemporary Psychophysics in New Directions in Psychology, New York: Holt, Rinehart and Winston, p. 97

7. Thresholds: Methods Method of Limits –Average of ascending and descending Method of Constant Stimuli –Stimuli randomized

8. Why Does an “Absolute” Threshold Vary? Internal Noise: Nervous system is always active Response Criterion: Person adopts different criteria, depending on their expectations

9. Signal-Detection Theory What determines a person’s report of a near-threshold stimulus? –Sensitivity: One’s ability to discriminate a stimulus from its background. –Response Criterion: The internal rule used to decide whether or not to report a stimulus.

10. Figure 3.3: The Absolute Threshold

11. Judging Differences Just-Noticeable Difference (JND): Smallest detectable difference between two stimuli. 10 grams11 grams StandardComparison JND = 1 gram

12. 10 grams 11 grams StandardComparisonJND 20 grams 22 grams 1 gram 2 grams 50 grams 55 grams5 grams 100 grams 110 grams10 grams 1000 grams 1100 grams100 grams

13. Weber’s Law Weber’s Law: JND is a constant fraction of intensity –JND = constant X intensity (in our case the constant is one-tenth) –As intensity increases, the JND increases in an geometrical fashion.

14. Vision

15. Figure 3.4: The Dimensions of a Wave

16. Electromagnetic Energy

17. Major Structures of the Eye

18. Retinal Image

19. Pathways from the Ganglion Cells into the Brain Douglas A. Bernstein, Louis A. Penner, Alison Clarke-Stewart, and Edward J. Roy, Psychology, Six Edition. Copyright © 2003 by Houghton Mifflin Company. Reprinted by permission.

20. Channels Night Vision (Rods) –Black and white –Low resolution –Rods Day Vision (Cones) –Color –High resolution –Cones

21. Cells in the Retina Douglas A. Bernstein, Louis A. Penner, Alison Clarke-Stewart, and Edward J. Roy, Psychology, Six Edition. Copyright © 2003 by Houghton Mifflin Company. Reprinted by permission.

24. Night Vision LightRodRhodopsin RetinalOpsin

27. Dark Adaptation

28. Bottom-Up Processing Retina (spots)

30. Ganglion Receptive Fields

31. From Sensation to Perception (Perceiving the letter “A”) Retina (spots) LGN of Thalamus (oriented bar) Occipital Lobe (oriented bar, anywhere) Temporal Lobe (associates bars together)

33. Cell Types Simple cell- bars of light, position sensitive, specific orientation, can be stationary (LGN). Complex cell- bars of light or dark, position insensitive, specific orientation, moving (Occipital). Hypercomplex cell- Similar to complex cell except but edges, corners, configuations (Occipital).