1. Chapter 1: Introduction to Perception

2. Why Study Perception? Future careers –Graduate school work in perception Medical applications –Devices to assist people with vision and hearing losses Understanding how you perceive the world –Language processing –Color vision –Depth perception

3. Figure 1-1 p5

4. Stimuli (Steps 1 and 2) Stimulus –Environmental stimulus are all objects in the environment are available to the observer. –Observer selectively attends to objects. –Stimulus impinges on receptors resulting in internal representation.

5. Figure 1-2 p6

6. Stimuli (Steps 1 and 2) - continued Principle of transformation –When the stimuli and responses created by stimuli are transformed, or changed, between the environmental stimuli and perception.

7. Receptor Processes/Transduction (Step 3) The process –Sensory receptors are cells specialized to respond to environmental energy –Visual pigment is what reacts to light –Transduction occurs which changes environmental energy to nerve impulses

8. Figure 1-3 p6

9. Neural Processing (Step 4) The process –Neural processing is the changes that occur as signals are transmitted through the maze of neurons. –Primary receiving area Occipital lobe Temporal lobe Parietal lobe

10. Figure 1-4 p7

11. Behavioral Responses (Step 5-7) Experience and Action –Perception occurs as a conscious experience. –Recognition occurs when an object is placed in a category giving it meaning. –Action occurs when the perceiver initiates motor activity in response to recognition.

12. Figure 1-5 p8

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14. Knowledge Knowledge is any information the perceiver brings to a situation. Bottom-up processing –Processing based on incoming stimuli from the environment –Also called data-based processing Top-down processing –Processing based on the perceiver ’ s previous knowledge (cognitive factors) –Also called knowledge-based processing

15. Figure 1-7 p9

16. Approaches to the Study of Perception Observing perceptual processes at different stages in the system: Psychophysical approach (Psychophysics) - the stimulus- perception relationship Physiological approach - the stimulus- physiology relationship Physiological approach - the physiology and perception relationship

17. Approaches to the Study of Perception - continued These stages are interconnected and communicate with one another. Cognitive influences on perception.

18. Figure 1-8 p10

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22. Measuring Perception Absolute threshold - smallest amount of energy needed to detect a stimulus –Method of limits Stimuli of different intensities presented in ascending and descending order Observer responds to whether she perceived the stimulus Cross-over point is the threshold

23. Figure 1-13 p12

24. Figure 1-15 p13

25. Measuring Thresholds Absolute threshold (cont.) –Method of adjustment –Stimulus intensity is adjusted continuously until observer detects it Repeated trials averaged for threshold

26. Measuring Thresholds - continued Absolute threshold –Method of constant stimuli Five to nine stimuli of different intensities are presented in random order Multiple trials are presented Threshold is the intensity that results in detection in 50% of trials.

27. Figure 1-16 p14

28. Measuring Thresholds - continued Difference Threshold (DL) - smallest difference between two stimuli a person can detect –Same methods can be used as for absolute threshold –As magnitude of stimulus increases, so does DL –Weber ’ s Law explains this relationship DL / S = K

29. Estimating Magnitude Magnitude estimation (scaling) –Stimuli are above threshold. –Observer is given a standard stimulus and a value for its intensity. –Observer compares the standard stimulus to test stimuli by assigning numbers relative to the standard.

31. Estimating Magnitude - continued Magnitude estimation (cont.) –Response compression As intensity increases, the perceived magnitude increases more slowly than the intensity. –Response expansion As intensity increases, the perceived magnitude increases more quickly than the intensity.

32. Figure 1-17 p15

33. Estimating Magnitude - continued Magnitude estimation (cont.) –Relationship between intensity and perceived magnitude is a power function –Steven ’ s Power Law P = KS n

34. Beyond Thresholds and Magnitudes Phenomenological method involves describe what they are perceiving or to indicate when a perception occurs Searching for stimuli –Visual search - observers look for one stimulus in a set of many stimuli Reaction time (RT) - time from presentation of stimulus to observer ’ s response is measured

35. Threshold Measurements Can Be Influenced by How a Person Chooses to Respond There are differences in response criteria among participants –Liberal responder - responds yes if there is the slightest possibility of experiencing the stimulus Response criterion is a persons individual response bias. Signal detection theory is used to take individual’s response criteria into account.

36. Figure 1-18 p16