6. Sensation & Perception presentation lecture

6. Sensation & Perception presentation lecture

1. SENSATION AND PERCEPTION

2. Sensation and Perception Detecting, Processing and Interpreting Experiences Sensory Receptors Sensory Thresholds Habituation and Sensory Adaptation The Sensory Organs Perceiving Sensory Stimuli

3. SENSATION the process of receiving stimulus energies from the external environment sensory organs: eyes (visual system) ears (auditory) nose (olfactory) tongue (gustatory) skin (tactile)

4. SENSATION The sense organ such as the eye, ears, skin, nose and tongue detect this energy and undergoes a process called TRANSDUCTION that transform the physical energy into a code that can be transmitted to the brain.

5. SENSATION Each of the sense organs has its own transducers. Retina – eye Cochlea – ears Skin receptors – skin Olfactory epithelium – nose Taste buds - tongue

6. PERCEPTION the process of organizing and interpreting sensory information to give it meaning . Prior experiences Expectations Memory Biases

7. Why is it important to study sensation and perception? The purpose of perception is: 1) to represent information from the outside world internally; 2) adaptation that improves a species’ chances for survival; and 3) to help in designing devices to restore perception to those who have lost some (or all) and also to devise treatments for other perceptual problems.

8. Have you ever experienced (or seen someone) bumping into a clear window glass because you did not know that it was there?

9. Psychophysics – is the field that studies links between the physical properties of stimuli and a persons experience of them.

10. “How far does my approaching boyfriend have to be before I smell his perfume?” “How different does the percentage of sugar have to be before I can taste the difference between the “zero-caloric” and “regular” versions of my favorite drink?”

11. Absolute Threshold Each one of us has an absolute threshold or the minimum amount or energy that we can detect

12. Absolute Threshold When a stimulus has a less energy than this absolute threshold, one cannot detect its presence.

13. BOTTOM-UP PROCESSING TOP-DOWN PROCESSING Sensory receptors register information about the external environment and send it up to the brain for analysis and interpretation. Starts out with cognitive processing at the higher levels of the brain. Cognitive processes include knowledge, beliefs and expectations.

14. JIGSAW PUZZLE

15. SENSORY RECEPTORS All sensation begins with sensory receptors. Sensory receptors are specialized cells that detect and transmit stimulus information to sensory nerves and the brain.

16. SENSORY THRESHOLDS Buzzing mosquito? Difference between regular Coke and Coke Zero?

17. SENSORY THRESHOLDS Absolute threshold Difference threshold Minimum amount of energy that a person can detect just noticeable difference ( jnd ) the degree of difference that must exist between two stimuli before the difference is detected.

18. SENSORY THRESHOLDS Difference threshold Is the smallest difference in stimulation required to discriminate one stimulus from another 50 % of the time. The difference threshold is the point at which a person reports that two stimuli are different 50 percent of the time.

19. 2 4 6 9 12 13

20. SENSORY THRESHOLDS Difference threshold An important aspect of difference thresholds is that the thresholds increases with the magnitude of stimulus.

21. 2 4 6 9 12 13

22. SENSORY THRESHOLDS Difference threshold One person may notice when a roommate turns up the volume of the stereo by even a small amount when the music is playing softly. But , if he/she turns the volume up an equal amount when the music is playing very loudly, one may not notice it

23. SENSORY THRESHOLDS E.H. WEBER (Weber’s Law) Regardless of magnitude, two stimuli must differ by a constant minimum percentage (rather than a constant amount) to be perceived as different.

24. SENSORY THRESHOLDS If one adds 1 candle to 60 candles, a difference in the brightness of the candles can be noticed. But when 1 candle is added to 120 candles one may not notice the difference. But when 2 candles are added to 120 candles, this time a difference may be noticed.

25. SENSORY THRESHOLDS Absolute Threshold Orange juice One tablespoon? Two tablespoon? Three tablespoon! Watching TV while your roommate is sleeping. Volume?

26. Approximate Absolute Thresholds Vision A candle flame at 30 miles on a dark, clear night. Hearing A ticking watch at 20 feet under quiet conditions. Smell One drop of perfume diffused throughout 3 rooms Taste A teaspoon of sugar in 2 gallons of water Touch The wing of a fly falling on your cheek from a distance of one centimeter.

27. Difference Threshold Watching TV while your roommate is sleeping. Your roommate, suddenly wakes-up. Also wants to watch the TV! Volume?

28. 2 4 6 9 12 13 No JND! JND!

29. A student late for his class. 10: 03 – late? 10:05 – late? 10: 10 – late? 10:15 – late!!! It takes 15 minutes for a student to be detected as late. Absolute or difference threshold? *Depends on the individual who perceives and the condition of the environment.

30. Subliminal Perception the ability to detect information below the level of conscious awareness. JAMES VICARY (1957) “Eat Popcorn”; “Drink Coke” .003 second once every 5 secs . The sales of popcorn and coke increased! HOAX! Subliminal perception does not work in advertising.

31. Subliminal Perception Can we sense stimuli that are below our absolute threshold?

32. Subliminal Perception Can we be affected by stimuli too weak for us ever to notice?

33. HABITUATION AND SENSORY ADAPTATION The lower centers of the brain sort through sensory stimulation and “ignore” or prevent conscious attention to stimuli that do not change. Sound of aircon Smell of garbage Reading your readings?

34. Sensory adaptation The sensory receptor cells become less responsive to an unchanging stimulus. The receptors are no longer sending signals to the brain. Habituation - The sensory receptor cells are still responding to the stimulus, but the lower centers of the brain are not sending the signals from those receptors in the cortex .

35. Sensory adaptation Entering your neighbor’s living room, you smell an unpleasant odor. You wonder how she tolerates the stench, but within minutes you no longer notice it. Jumping into swimming pool, you shiver and complain how cold it is. A short while later a friend arrives and you exclaim, “C’mon in. Water’s lovely!”

36. QUESTIONS?