Sensation and Perception

1. Sensation and Perception Chapter 3 George S. Robinson, Jr., Ph.D. Department of Psychology North Carolina A&T State University

2. Sensation and Perception • Sensation • activation of receptors by stimuli • Perception • organizing and interpreting sensory information • Transduction • converting stimuli from the receptors to an electrochemical pattern • Adaptation • loss of sensitivity to a stimulus due to repeated stimulation of a receptor

3. Sensation and Perception

4. Psychophysics • Psychophysics • the relationship between stimuli and the participant’s experience • Absolute threshold • minimum amount of energy of a stimulus that can be detected 50 percent of the time • Weber’s Law • the size of a just noticeable difference is a constant proportion of the size of the initial stimulus • Just Noticeable Difference (JND) • smallest difference between two stimuli that can be detected 50 percent of the time

5. Signal Detection Theory • A threshold varies with the nature of the stimulus (signal) and background stimulation (noise)

6. The Visual Stimulus • Wavelength • Amplitude • saturation • radiant light • reflected light

7. Visual System • Accommodation • conjunctive eye movements • vergence eye movements • retina • rods • cones • fovea • bipolar cells • blind spot • optic chiasm

8. Visual System - cont.

9. Theories of Color Vision • Trichromatic theory (Young-Helmholtz) • there are three types of color receptors

10. Theories of Color Vision - cont • The Opponent Process Theory • red - green • when red is active green is inhibited and vice versa • bleu - yellow • when blue is active yellow is inhibited and vice versa • color after images • perception of color that is not really present; occurs after viewing the opposite or complimentary color

11. Color Afterimage • Focus on the dot in the center of the flag for 30 seconds – auto advance

13. Color Deficiencies • Monochromat • person who sees only shades of gray; very rare • Dichromat • person who has trouble seeing one of the primary colors (red, green or blue) • Anomalous trichromat • form of colorblindness in which one of the three primary colors (red, green or blue) is processed incorrectly

14. Test of Color Deficiency

15. The Auditory Stimulus • Wavelength (frequency, Hertz) • amplitude (intensity, Decibel) • Purity (timbre) • Hearing range 20 - 20,000 Hertz

16. The Auditory System • Pinna • Auditory canal • Eardrum • Ossicles • hammer (malleus), anvil (incus), stirrup (stapes) • Oval window • Basilar membrane • Organ of Corti • Tectorial membrane • place theory • frequency theory

17. Hearing Disorders • Conduction deafness • deafness from transmitting sound through the outer and middle ear • Sensorineural deafness • deafness from damage to the inner ear, especially the hair cells • central deafness • deafness caused by disease and tumors in the auditory pathways or auditory cortex

18. Sounds and Damage to the Auditory System

19. Taste (Gustation) • Taste buds • structures that contain the taste receptors, each bud contains about 20 receptors • Papillae • bumps on the tongue and in the throat that are lined with taste buds • Microvilli • hairs that project from taste buds

20. Taste - cont.

21. Smell (Olfaction) • Olfactory bulb • Olfactory receptors • cilia • 100 different type of receptors • lock-and-key • pattern of receptors

22. Other Sensory Systems • Vestibular Sense • allows us to make adjustments to bodily movements and posture • semicircular canals • fluid filled passages in the inner ear • utricle • fluid filled chamber in the inner ear that detects changes in gravity

23. Other Sensory Systems - cont. • Kinesthetic sense • receptors located in the muscles and joints that provide information about the location of the extremities • Somatosensory Processing • mechanoreceptors - touch or pressure • thermoreceptors - temperature receptors

24. Other Sensory Systems - cont. • Skin receptors • Meissner corpuscles • light touch • Merkel Disks • steady pressure • Ruffini endings • pressure of large objects, stretching of the skin • Pacinian corpuscles • very sensitive to touch • Free nerve endings • temperature and pain

25. Sensitivity to Touch

26. Other Sensory Systems - cont. • Pain • nocioreceptors • receptors that respond to painful stimuli • gate control theory • endorphins • substance P

27. Perception • Motivational influences • Attention • divided attention • dichotic listening

28. Perception - cont. • Patterns and Constancies • pattern perception • feature detectors • feature analysis theory • we perceive basic elements of an object, and assemble them mentally to create a whole • bottom-up approach (model) • top-down approach (model)

29. Pattern and Constancies - cont • Perceptual constancies • shape constancy • size constancy • Depth Perception • binocular cues • convergence (eye muscles) • binocular (retinal) disparity • Monocular cues • superimposition, texture gradient, linear perspective, relative brightness

30. Depth Perception - Visual Cliff

31. Gestalt Principles of Perceptual Organization • Figure-ground relationships

32. Gestalt Principles of Grouping • Proximity • similarity • continuation • closure • inclusiveness

33. Perception of Movement • Apparent Motion (autokinetic effect) • illusion of movement in a stationary object • television • movies • video games

34. Perceptual Hypothesis and Illusions • Perceptual hypothesis • inferences about the nature of stimuli received from the environment • Perceptual illusions • misperceptions or interpretations of stimuli that do not correspond to the sensations received

35. Perceptual Illusions

36. Perceptual Illusions - cont.

37. Extrasensory Perception (ESP) • Clairvoyance • to see hidden objects • telepathy • to perceive the thoughts or emotions of others • Precognition • knowledge of the future • Psychokinesis (telekinesis) • ability of the mind to influence matter

38. Click on the “X” in the top right corner to close the program Select YES at the WARNING prompt to test your ESP • Zener cards • Ganzfeld (“total field”)