Sensation and Perception Chapter 4

1. Sensation and PerceptionChapter 4 George S. Robinson, Jr., Ph.D. Department of Psychology North Carolina A&T State University

2. How Many Faces Can You Perceive?

3. Understanding your reality What is real? Ultimately, reality is determined by what one perceives. That is, you create your own reality. Qualitative is necessarily subjective Qualia = the subjective quality of conscious experience Construct = Create “residual self-image” Electrical signals interpreted by the brain “neural interactive simulation” – dream world | What is a dream? What is consciousness?

4. Sensation and Perception • Sensation • is the stimulation of sense organs • Perception • is the selection, organization, and interpretation of sensory input

5. Sensation and Perception

7. Psychophysics • Psychophysics • the study of how physical stimuli are translated into psychological experience • threshold • a dividing point between energy levels that do and do not have a detectable effect • absolute threshold • a minimum amount of stimulation that an organism can detect 50% of the time • Just Noticeable Difference (JND) • the smallest difference in the amount of stimulation that a specific sense can detect

8. Psychophysics - cont. • Signal Detection Theory • proposes that the detection of stimuli involves decision processes as well as sensory processes, which are both influenced by a variety of factors besides stimulus intensity • based on environmental and neural noise as well as expectations • hits - detecting signals when they are present • misses - failing to detect signals when they are present • false alarms - detecting signals when they are not present • correct rejections - not detecting signals when they are absent • (e.g., military applications > “friendly fire”, “friendly attack”, “collateral damage”; Air Traffic Controllers > planes on a radar screen)

9. Signal Detection Theory

10. Psychophysics - cont. • Subliminal Perception • the registration of sensory input without conscious awareness • Sensory Adaptation • a gradual decline in sensitivity to prolonged stimulation

11. Our Sense of Sight: The Visual System • Light • electromagnetic radiation that travels as a wave • wavelength (distance between peaks; color) • amplitude (height; brightness) • purity (how varied the mix is; saturation or richness of colors)

12. Electromagnetic Radiation

13. Our Sense of Sight: The Visual System - cont. • The Eye • cornea, pupil, iris, lens • retina • rods, cones, fovea, • optic disk (blind spot), • optic nerve

14. Our Sense of Sight: The Visual System - cont. • nearsightedness - close objects seen clear, but distance objects are blurry • farsightedness - distant objects are seen clearly, but close objects appear blurry • dark adaptation - the eyes become more sensitive to light in low illumination (e.g., entering a dark theater) • light adaptation - the eyes become less sensitive to light in high illumination (e.g., coming out of a dark theater) • receptive field - the retinal area that when stimulated affects the firing of that cell • lateral antagonism (inhibition) - neural activity in a cell opposes activity in surrounding cells • contrast, edge detection

15. Hermann Grid (Lateral Antagonism)

16. Visual Pathways to the Brain • Optic chiasm • Optic tract • Lateral geniculate nucleus (LGN) • Primary visual cortex • Superior colliculus • Magnocellular • motion, depth and brightness • Dorsal stream – the “Where Pathway” • Parvocellular • color, form and texture • Ventral stream - the “What Pathway”

17. Information Processing in the Visual Cortex • Simple cells – respond best to a line of the correct width, angle, and spatial location • Complex cells – respond to any position in the receptive field, and movement • Feature detectors – neurons that respond selectively to very specific features of more complex stimuli • Visual agnosia – an inability to recognize objects • Prosopagnosia – an inability to recognize familiar faces

18. Color Vision • Trichromatic theory of color vision (Young – Helmholtz) • Three types of cones; • red, green and blue (RGB) • Color blindness • Dichromats – only two color channels • Monochromats • can not see any colors

19. Color Vision – cont. Opponent process theory of color vision Opponent pairs; red-green, blue-yellow, black-white Complimentary colors pairs of colors that produce gray when mixed together Afterimage a visual image that persists after a stimulus is removed

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

22. Perceiving Forms, Patterns, and Objects • Reversible figure • Perceptual set • Inattentional blindness • Feature analysis (detection) • Bottom-up processing • Top-down processing • Subjective contours • Gestalt principles • Phi phenomenon • Figure and ground • proximity, closure, similarity, simplicity, continuity • Formulating perceptual hypotheses • Distal stimuli – stimuli that lie in the distance • Proximal stimuli – the stimulus energy that impinge directly on the sensory receptors • Perceptual hypothesis – an inference about which distal stimuli could be responsible for the proximal stimuli

23. How many faces can you perceive?

24. Four faces – Original Advertisement

25. Depth Perception – Visual Cliff

26. Perceiving Depth or Distance • Depth perception • Involves interpretation of visual cues that indicate how near or far away objects are • Binocular cues • Retinal disparity • Convergence • Monocular cues • Pictorial depth cues • Linear perspective, texture gradients, interposition, relative size, height in plane, light and shadow • Perceptual constancies in vision • Size constancy, shape constancy, brightness constancy, color constancy • Optical Illusions

27. Optical Illusions

28. Optical Illusion – cont.

29. Extra Sensory Perception • 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

30. 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

31. Our Sense of Hearing: The Auditory System • Sound • Wavelength (frequency) – pitch • human range from 20 – 20,000 hertz (Hz) • Amplitude (decibel) – loudness • Wave purity - timbre

32. Our Sense of Hearing: The Auditory System – cont. • The ear • External ear • Pinna, auditory canal • Middle ear • Eardrum, hammer (malleus) • , anvil (incus), stirrup (stapes) • Inner ear • Oval window, cochlea, basilar membrane, hair cells

33. Our Sense of Hearing: The Auditory System – cont. • Theories of hearing • Place theory • Frequency theory • Loudness is coded by the number of receptors that fire • Low intensity = few receptors firing • High intensity = many receptors firing • Conductive hearing loss • Nerve deafness • Auditory localization: Perceiving Sources of Sound • Intensity (loudness) • Time of the sound arriving at each ear

34. Place Theory

35. Sound and Damage to the Auditory System

36. Our Chemical Senses: Taste and Smell • Taste: The Gustatory System • Taste buds • 10,000 taste buds • each taste bud contains • 12 or more taste cells • Primary tastes • Sweet (tip of the tongue) • sour (upper side) • bitter (back part of the tongue) • salty (middle side)

37. Smell • Smell: The Olfactory System • Olfactory bulb • Olfactory cilia

38. Our Sense of Touch: Sensory Systems in the Skin • Touch • Free nerve endings (pressure, temperature, and pain) • Hot and cold fibers • Pain • C-fibers (unmyelinated, slow pathway, carries dull, burning or aching pain) • A-delta fibers (myelinated, fast pathway, carries sharp pain) • Gate control theory • Endorphins

39. Our Other Senses • Kinesthetic System • Monitors the positions of the various parts of the body • Receptors in the muscles, joints, and skin provide information about movement, posture, and orientation • Vestibular System • Responds to gravity and keeps you informed of your body’s location in space • Semicircular canals