Module 11 Introduction to Sensation and Perception

1. Module 11 Introduction to Sensation and Perception

2. Sensation • Sensation • the process by which our sensory receptors and nervous system receive and represent stimulus energy • Perception • the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events

3. Sensation • Sensation how do we change energy into sense • Perception what do we do with our sensory information

4. Sensation • Our sensory and perceptual processes work together to help us sort out complex images

5. Sensation • Bottom-Up Processing • analysis that begins with the sense receptors and works up to the brain’s integration of sensory information (piecing lines together to recognize the number 4) • Top-Down Processing • information processing guided by higher-level mental processes • as when we construct perceptions drawing on our experience and expectations (think you know someone and as they get closer, realize that you don’t)

6. Sensation- Basic Principles • Psychophysics • study of the relationship between physical characteristics of stimuli and our psychological experience of them • Light- brightness • Sound- volume • Pressure- weight • Taste- sweetness

7. Sensation- Thresholds • Absolute Threshold • minimum stimulation needed to detect a particular stimulus 50% of the time • isn’t constant – can change with motivation and alertness • Difference Threshold • minimum difference between two stimuli required for detection 50% of the time • just noticeable difference (JND)

8. Sensation- A. Thresholds • Signal Detection Theory • predicts how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise) • assumes that there is no single absolute threshold • detection depends partly on person’s • experience • expectations • motivation • level of fatigue

9. Sensation- A. Thresholds • Signal Detection Theory detection of stimuli involves decision processes as well as sensory processes Example – riddle, shower/telephone

10. “You’re driving a bus with 12 passengers. At your first stop, 6 passengers get off. At the second stop, 3 get off. At the third stop, 2 more get off, but 3 new people get on. What color are the driver’s eyes? Did you detect the signal – who is the driver? – over the noise – number of passengers?

11. 100 Percentage of correct detections 75 50 Subliminal stimuli 25 0 Low Absolute threshold Medium Intensity of stimulus Sensation- A. Thresholds • Subliminal • when stimuli are below one’s absolute threshold for conscious awareness

12. Sensation- A. Thresholds Subliminal Messages Reverse Speech - Voices From The Unconscious

13. Sensation- Thresholds • Difference Threshold • minimum difference between two stimuli required for detection 50% of the time • just noticeable difference (JND) – we experience the difference threshold as a JND.

14. Read the passage at the right. • How many lines do you require to experience a noticeable difference?

15. Sensation- D. Thresholds • Weber’s Law • to be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount) • light intensity- 8% (1/60) • weight- 2% (1/50) • tone frequency- 0.3% (1/333)

16. Sensation- D. Thresholds • Sensory Adaptation • diminished sensitivity as a consequence of constant stimulation (wearing a new wristwatch) • Selective Attention • focusing of conscious awareness on a particular stimulus • as in the cocktail party effect (listen to one voice, among many)

17. Now you see it, now you don’t!

18. Perception • Selective Attention Do you see circles with white lines or a cube? Because attention is selective, you only see one interpretation at a time.

19. Change Blindness • Change Blindness is an example of Selective Attention Lab Demos

20. Change Blindness