SENSATION & PERCEPTION

1. CHAPTER 4 SENSATION& PERCEPTION

2. Sensation & Perception • Sensation: How energy from the world is converted into neural impulses our brain can understand. • Perception: How our brain selects, organizes, and interprets our sensations.

3. Psychophysics • The study of how the physical world is interpreted by our brains.

4. Sensory Receptors • Specialized cells that detect stimulus information and transmit it to sensory (afferent) nerves and the brain. • Classes • A) Photoreception- detection of light perceived as sight • B) Mechanoreception- detection of pressure, vibration, and movement, perceived as touch, hearing, and equilibrium. • C) Chemoreception- detection of chemical stimuli, perceived as smell and taste.

5. Absolute Threshold Difference Threshold • Minimum stimulation needed to detect a particular stimulus 50% of the time. • Examples • Vision: a flame from a single candle 30 miles away • Hearing: ticking of a watch 20 feet away • Touch: an ant walking on your arm • Minimum difference between two stimuli required for detection 50% of the time, also called just noticeable difference (JND). • Examples • You turn the temperature down from 74 degrees to 73 degrees, and all of a sudden someone in the house is cold. • Your change the volume of the car by one level and someone complains that its too loud. Thresholds

6. Subliminal Threshold: When stimuli are below one’s absolute threshold for conscious awareness. Subliminal Threshold

7. Weber’s Law Fechner’s Law • The size of a JND is proportional to the type of stimulus. • PERCEIVED magnitude of a JND scales with the number of JND’s added • Example • You walk into a dark room • You turn on one lamp – the difference between dark and light is HUGE • Then you turn on another lamp… its twice the light, but not twice as bright • Then you turn on a third lamp and barley notice any difference in lighting Scaling

8. Signal-Detection Theory • Our ability to discriminate (tell the difference) between ‘noises’. • Detection depends on: • Person’s experience • Expectations • Motivation • Level of fatigue

9. Sensory Adaptation • Gradual decline in sensitivity with constant stimulation • Example: • Wearing a watch • The clothes on your back

10. VISION!

11. Transduction • The transformation of stimulus energy into neural impulses.

12. Light • Phototransduction begins with light energy. • Light has three characteristics: • Wavelength (hue/color) • Wider = Red • Narrower = Blue • Amplitude (brightness) • Taller = Brighter • Shorter = Duller • Purity (saturation/richness of color)

13. The Eye

14. The Lens • Accommodation: The process by which the eye’s lens changes shape to help focus near or far objects on the retina.

15. Retina

16. Rods Cones • Long • 100-125 million • Peripheral vision and night vision (Rods=Raccoons) • Sensitive to dim light • Outnumber cones in periphery of retina • Short • 5-6.4 million • Cones = Color vision and daylight vision • Don’t respond well to dim light • Provide more sharp and detailed vision • Concentrated in center of retina (fovea only cones) Photoreceptors

17. Fovea

18. Vision Issues • Nearsightedness: A condition in which nearby objects are seen more clearly than distant objects. • Farsightedness:A condition in which faraway objects are seen more clearly than near objects.

19. Optic Chiasm

20. Vision in the Brain • Parallel processing • Your brain now uses the same information to do multiple things • Example • determine color & brightness • Feature detectors • Neurons that respond to certain types of stimuli • Example • You have neurons that help you recognize what a face looks like

21. Theories of Color Vision • Trichromatic theory • The retina contains three receptors that are sensitive to red, blue and green colors.

22. Addition of Colors If three primary colors (lights) are mixed, the wavelengths are added and the color white is the result.

23. Subtraction of Colors If three primary colors (pigments) are mixed, subtraction of all wavelengths occurs and the color black is the result.

24. Color Blindness Genetic disorder in which people are blind to green or red colors. This supports the Trichromatic theory.

25. Opponent Process Theory We process primary colors combined in three pairs of red-green, blue-yellow, and black-white.

26. AUDITION!

27. Sound • Acoustical transduction begins with sound energy. • Sound has three characteristics: • Frequency (pitch) = wavelength • Intensity (loudness) = wave amplitude • Quality (timbre) = uniqueness of sound

28. The Ear

29. Cochlea

30. Place Theory Frequency Theory • Says sound frequencies stimulate the basilar membrane at specific places resulting in perceived pitch. • Says that the speed of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to know its pitch Theories of Audition

31. Localization of Sounds • We have two ears • Sounds may reach one ear faster than the other ear • Or sounds may be louder in one ear than another • This let’s us locate the sound • Our head acts as a “shadow”

32. Deafness • Conduction Hearing Loss • Caused by damage to the parts of the ear that connect to the cochlea • Sensorineural Hearing Loss • Caused by damage to the cochlea or to the auditory nerve

33. Touch • The sense of touch is a mix of four distinct skin senses • pressure, warmth, cold, and pain • Extreme heat & extreme cold are THE SAME!

34. Pain • Pain tells the body that something has gone wrong. • CIP (Congenital Insensitivity to Pain) • A rare disease in which the afflicted person feels no pain.

35. Gate-Control Theory • Proposes that our spinal cord contains “gates” that either block pain or allow it to be sensed.

36. Taste • A chemical sense • Originally, it was believed the tongue had 4 taste receptors: • sweet, salty, sour, and bitter • Receptors for a fifth taste have been discovered • “Umami”

37. Smell • A chemical sense • Also known as Olfaction • Odors enter the nasal cavity to stimulate Olfactory receptors

38. Flavor • Combination of taste and smell • Example: • Strawberries are sweet • But smell is what distinguishes a strawberry from a blueberry

39. Kinesthesis • Knowing where our body parts are located at all times

40. Vestibular Sense • Our sense of balance • Located in the inner ear • Monitors head and body position

41. perception

42. BOTTOM-UP PROCESSING • Sensory receptors register information about the external environment and send it up to the brain for interpretation. • A progression from individual elements to the whole. • More accurate, slower • Feature analysis

43. TOP-DOWN PROCESSING • Launched by cognitive processing at the brain’s higher levels, that allows the organism to sense what is happening and to apply the framework to the information from the world. • A progression from the whole to the elements. • Faster, error prone • Gestalt principles • Perceptual set

45. Principles of Perception • Distal stimuli • The world outside the body • Proximal stimuli • The energy received by our senses

46. Selective Attention • We can only pay attention to one thing at a time, but that doesn’t mean we can’t constantly change our perceptions of the world around us. • This is what allows us to see reversible figures.

47. PERCEPTUAL SET • A predisposition or readiness to perceive something in a particular way. • expectancy

48. GESTALT PSYCHOLOGY • School of thought interested in how people naturally organize their perceptions according to certain patterns. • Emphasizes that the whole is greater than the sum of its parts. • Max Wertheimer

49. GESTALT PRINCIPLES • Used to explain how we perceive objects. • Figure-ground • Proximity • Closure • Similarity • Simplicity • Continuity

50. FIGURE AND GROUND