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3-1
4th Edition
Sensation and Perception
Chapter 3
3-2
Sensation, Perception and Psychophysics
• Vision
• Hearing
• Taste
• Smell
• Body position
• Movement
We receive and process information about:
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Sensation, Perception and Psychophysics
• Sensation refers to stimulation or activation of the receptors.
• Perception is the organization of what you have sensed.
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Sensation, Perception and Psychophysics
• Receptors for each sensory system respond to only one type of environmental stimulus.
• Transduction – physical properties are converted to a form we can perceive.
• Adaptation occurs when continued presentation of the same stimulus results in a loss of sensitivity.
3-5
Sensation, Perception and Psychophysics
• Psychophysicists, such as Ernst Weber and Gustav Fechner, studied the relationship between the mind and the body.
• Weber: Just noticeable difference (jnd) – The smallest amount of energy that must be added or subtracted to detect change 50% of the time
• Absolute Threshold
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Sensory SystemsVision
• Light waves differ in terms of wavelength (hue) or color, anplitude (intensity), and saturation (purity).
• The psychological counterpart of wavelength is color.
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Sensory SystemsVision
• Saturation = “trueness” of only one hue.
• Amplitude = intensity.
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Additive and Subtractive Processes of Color Mixing
• Radiant light is visible energy emitted by an object• Reflected light is light waves that are reflected from
objects
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Sensory SystemsVision
• Sensory systems of the eye consists of Rods and Cones. –The cones have greater acuity, respond to color, and have a higher threshold for activation.About 120 million per eye.
–The rods have lower acuity, respond to black and white and shades of gray, and have a lower threshold.About 7 million per eye.
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Sensory SystemsVision
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Sensory Systems
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Sensory SystemsVisual Pathways
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Two theories of color vision
• The trichromatic theory proposes that there are three different types of cones;
• The opponent-process theory argues that color-sensitive cells are arranged in pairs.
• Both theories are supported by research findings.
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Opponent-process Theory
Pairs of Yellow-Blue and Red-Green Cones
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Color Blindness
• Dichromats lack the ability to see one of the three primary colors.
• Monochromats are unable to see color.
IshiharaPlate
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Sensory SystemsAudition
• Audition is initiated by the movement of molecules in the air.
• Varies by wavelength (frequency), amplitude (intensity), and purity (timbre)
• Vibration of the eardrum starts a chain reaction that results in movement of fluid in the inner ear and the bending of specialized hair cells, which are the receptors for hearing.
3-17
Sensory Systems
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Hearing Disorders
Conduction deafness
Sensorineural deafness
Central deafness
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Sensory SystemsGustation
• Molecules in solution stimulate taste.
• Hairs on taste buds, serve as the receptors.
• Each receptors may respond to several tastes, but each one is maximally sensitive to one of four tastes salty, sweet, sour, or bitter. Some people add metallic and alkaline
3-20
Gustation
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Sensory Systems
• Molecules in the air stimulate the sense of smell.
• Hairs located in the nasal cavity serve as the receptors.
• Olfaction has a direct connection to the limbic system [next]
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Sensory Systems Vestibular Sense
• The vestibular sense enables us to adjust to different bodily movements.
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Sensory Systems Kinesthetic Sense
• The kinesthetic sense allows us to determine the position of our extremities.
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Sensory SystemsCutaneous Senses
• Mechanoreceptors• Nocioreceptors• Thermoreceptors
Cutaneous receptors for pressure, pain, and temperature are located in the skin.
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Perception
• We engage in selective attention because we cannot process all of the stimuli we encounter.
• Dichotic listening experiments study divided attention.
• With practice we can learn how to divide our attention effectively.
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PerceptionSize Constancy
• We experience perceptual constancies when our perception of an object does not change, even though the retinal image.
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Shape Constancy
Perception of shape remains constant even though image on retina changes.
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Depth Perception and Binocular Disparity
Close objects translate very fast (brush) and distant objects pass very slow (mountains).
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Gestalt Principles of Perception
• We actively organize our perceptual world into meaningful groups or wholes.
• The figure-ground relation is one of the most basic perceptual organizations.
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Gestalt Principles of Perception
Proximity
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Perception
• Perceptual hypotheses are inferences about the nature of the stimuli we sense.
• Perceptual illusions and ambiguous figures may cause us to develop incorrect perceptual hypotheses.
• Hermann grid
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Ames Room
In the Ames Room, even the size of a familiar object (such as a person) is perceived largely distorted, because the misleading geometry generates an incorrect frame of reference
3-33
Zener Cards
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Skeptics
Zener Cards, ESP, Telekinesis