Sensation and Perception chapter 6

1. Sensation and Perceptionchapter 6 Sensation: your window to the world Perception: interpreting what comes in your window.

2. Sensation • The process by which our sensory receptors and nervous system receive stimulus from the environment. (stuff inputed from our 5 senses)

3. Bottom-Up processing • a progression from individual elements to the whole (start small then work your way up). Visually, that would mean noticing lines, angles, colors etc. • Basically……..Sensory detection

4. Top-Down processing • Start with the forest and work your attention down to the individual tree. • Basically…..the brain’s perception of what the info brought in by the 5 senses!!! The meaning!

5. Absolute Threshold • The minimum stimulation needed to detect a stimulus 50% of the time. • EX: the flame of a candle on a clear night 30 miles away

6. Signal detection • Detecting the presence of a faint stimulus amid background stimulus. • It depends on our psychological state (alertness, expectations, experiences, motivations) • EX: hearing a crying infant is lower when you become a parent!

7. Subliminal stimuli • Can we sense stimuli below our absolute thresholds? YES • Can advertisers influence us with “subliminal messages”? Not really • How does it affect us? It can prime us. • In one experiment, subliminally emotionally positive scenes (kittens…) or negative scenes (dead body) were flashed before viewing a pic of a face. Those faces that had a flash of a postive image (which to them looked like a flash of light) rated the faces as nicer.

8. Difference threshold • The least amount of stimulation needed to notice that a change has taken place • Important for certain tasks like piano tuning • EX: knowing your child’s voice among all the other’s

9. Weber’s Law • The idea that, to perceive a difference between two stimuli, they must differ by a constant percentage; not a constant amount • Ex: Which would you notice on a purchase of a $20,000 car? Car mats- $100 Backseat DVD player $500 Alloy wheels $2000 Window tinting- $200

10. Sensory Adaptation • Our sensitivity to unchanging stimuli gradually diminishes • Why do the senses seem to attend only to novel stimuli? Do you feel your underwear all day?

11. Question: • If sensory adaptation occurs, why then, if we stare at an object, does it not vanish from sight? • Answer: The eye constantly quivers to counteract this possibility…we just don’t realize it!!!

12. Selective Attention • The focusing of conscious awareness on a particular stimulus. • The brain really only focuses on ONE main thing at a time!!!!!

13. Selective Attention • The brain makes what you focus on the foreground and everything else the background. • Can you switch these??

14. An example of selective attention is: Cocktail Part Effect: ability to listen to one voice among many.

15. Vision • Vision-Our most dominating sense. • Visual Capture-this is why we fall for ventriloquists

16. Phase One: Gathering Light • The height of a wave gives us it’s intensity (brightness). • The length of the wave gives us it’s hue (color). • ROY G BIV • The longer the wave the more red. • The shorter the wavelength the more violet.

17. Transduction • Transforming signals into neural impulses. Information goes from the senses to the thalamus , then to the various areas in the brain.

18. Phase Two: Getting the light in the eye

19. Phase Three: Transduction

20. Order of cells in the retina • rods, cones bipolar cells ganglion cells • Can you create a way to recall their order? R C B G

21. Phase Four: In the Brain • Goes to the Visual Cortex located in the Occipital Lobe of the Cerebral Cortex. • Feature Detectors. • Parallel Processing We have specific cells that see the lines, motion, curves and other features of this turkey. These cells are called feature detectors.

22. What are feature detectors? We have specific cells in the brain that see the lines, motion, curves and other features of this turkey. These cells are called feature detectors.

23. Motion detectors • For example, there are motion detector cells that fire for a variety of motions. Here’s one for movement. • Let’s see what happens when we over use them: stare at the center of this for 30 sec. • http://www.michaelbach.de/ot/mot_adaptSpiral/index.html

24. What is parallel processing? • Brain’s ability to perceive several features simultaneously Example: • movement • Color • Size • direction

25. Color Vision Two Major Theories

26. Trichromatic Theory Three types of cones: • Red • Blue • Green • These three types of cones can make millions of combinations of colors.

27. Opponent-Process Theory • We cannot see certain colors together in combination (red-green, blue-yellow, and white-black). These are antagonist/ opponent colors. It explains afterimages! Tube and marble example.

29. Amplitudeis how loud the sound is. The higher the crest of the wave is the louder the sound is. It is measured in decibels.

32. Cilia- receptors cells in the ear

33. Transduction in the ear It is all about the vibrations!!! Sound waves hit the eardrum then anvil then hammer then stirrup then oval window. Everything is just vibrating. Then the cochlea vibrates. The cochlea is lined with mucus called basilar membrane. In basilar membrane there are hair cells called cilia. When the cilia vibrate, they turn vibrations into neural impulses.

34. How do we perceive differences in pitch? There are two theories……..

35. 1. Helmholtz’s Place Theory • We hear different pitches because different sound waves trigger activity at different places along the cochlea’s basilar membrane.

36. The Place Theory • Only explains HIGH pitches!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

37. 2. Frequency Theory • We sense pitch by the basilar membrane vibrating at the same rate as the sound. • Only explains LOW pitches!!!!!!!!

38. So….what about all the pitches in between????? • This problem can be explained using the volley principle. • Between the two (place and frequency) they think the brain figures out the ones in between…..

39. Why do we have two ears? • To determine the direction of a sound!!!!

40. Two types of hearing loss: 1. Conduction Hearing Loss: caused by damage to mechanical system of ear (little bones). 2. Sensorinueral hearing loss: caused by damage to cochlea’s receptor cells or to auditory nerves.

41. Which type of hearing loss would be due to age? • Why?

42. Which type would be due to the accumulated exposure to loud sounds?

43. Smell and Taste Why do we study smell and taste together?

44. SENSORY INTERACTION: smell and taste • the principle that one sense may influence another. • Taste and smell are chemical senses.

45. Taste We have bumps on our tongue called papillae. Taste buds are located on the papillae (they are actually all over the mouth). Sweet, salty, sour and bitter.

46. Does “Sweet N. Low Taste Bitter?Are You a Picky Eater? Maybe you’re a “supertaster”!!! • http://courses.bfwpub.com/myers9e

47. PTC Strips

48. Sensitivity to taste • Decreases due to: Smoking Drinking age

49. But what about smell? It is a chemical sense What are the receptor cells for smell? Cilia in your nose.