© 2013 the mcgraw-hill companies, inc. all rights reserved. sensation and perception chapter 3

© 2013 The McGraw-Hill Companies, Inc. All rights reserved.

Sensation and Sensation and PerceptionPerception

Sensation and Sensation and PerceptionPerception

Chapter 3Chapter 3

© 2013 The McGraw-Hill Companies, Inc. All rights reserved.2

Sensing the World Around UsSensing the World Around UsSensing the World Around UsSensing the World Around Us

• Learning Outcomes– Define absolute thresholds– Explain the difference threshold and Weber’s law– Discuss sensory adaptation

• Learning Outcomes– Define absolute thresholds– Explain the difference threshold and Weber’s law– Discuss sensory adaptation


Absolute ThresholdsAbsolute ThresholdsAbsolute ThresholdsAbsolute Thresholds

• Absolute threshold: the smallest intensity of a stimulus that must be present for it to be detected

• Absolute threshold: the smallest intensity of a stimulus that must be present for it to be detected


Difference ThresholdsDifference ThresholdsDifference ThresholdsDifference Thresholds

• Difference threshold (just noticeable difference)

• Weber’s law

• Difference threshold (just noticeable difference)

• Weber’s law


Sensory AdaptationSensory AdaptationSensory AdaptationSensory Adaptation

• Sensory adaptation: an adjustment to sensory capacity when stimuli in the environment are unchanging; “getting used to” a sensory stimulus so that you no longer have the same reaction to it as you initially did

• Sensory adaptation: an adjustment to sensory capacity when stimuli in the environment are unchanging; “getting used to” a sensory stimulus so that you no longer have the same reaction to it as you initially did


Vision: Shedding Light on Our EyeVision: Shedding Light on Our EyeVision: Shedding Light on Our EyeVision: Shedding Light on Our Eye

• Learning Outcomes– Explain the basic structure of the eye– Compare and contrast color vision with color

blindness

• Learning Outcomes– Explain the basic structure of the eye– Compare and contrast color vision with color

blindness


The Structure of the EyeThe Structure of the EyeThe Structure of the EyeThe Structure of the Eye

• Light passes through the cornea, pupil, and the lens before reaching the retina: converts the energy of the light to electrical impulses for transmission to the brain– Rods– Cones– Optic Nerve– Feature Detection

• Light passes through the cornea, pupil, and the lens before reaching the retina: converts the energy of the light to electrical impulses for transmission to the brain– Rods– Cones– Optic Nerve– Feature Detection


Figure 2Figure 2Figure 2Figure 2


Color Vision and Color BlindnessColor Vision and Color BlindnessColor Vision and Color BlindnessColor Vision and Color Blindness

• Trichromatic theory of color vision: three kinds of cones exist in the retina (one most responsive to blue-violet, one to green, & one to yellow-red)

• Trichromatic theory of color vision: three kinds of cones exist in the retina (one most responsive to blue-violet, one to green, & one to yellow-red)


Color Vision and Color BlindnessColor Vision and Color BlindnessColor Vision and Color BlindnessColor Vision and Color Blindness

• Opponent-process theory of color vision: receptor cells are linked in pairs (blue-yellow, red-green, & black-white), working in opposition to each other

• Opponent-process theory of color vision: receptor cells are linked in pairs (blue-yellow, red-green, & black-white), working in opposition to each other


Hearing and the Other SensesHearing and the Other SensesHearing and the Other SensesHearing and the Other Senses

• Learning Outcomes– Describe how we sense sound– Discuss smell and taste– Distinguish the skin senses

• Learning Outcomes– Describe how we sense sound– Discuss smell and taste– Distinguish the skin senses


Sensing SoundSensing SoundSensing SoundSensing Sound

• Sound: movement of air molecules brought about by vibration (sound waves)

• Semicircular canals: movement of fluid here affects our sense of balance

• Sound: movement of air molecules brought about by vibration (sound waves)

• Semicircular canals: movement of fluid here affects our sense of balance


Smell and TasteSmell and TasteSmell and TasteSmell and Taste

• Smell (olfaction)– Molecules enter the nasal passages and pass over

olfactory cells (receptor neurons); responses sent to brain, where they are combined for recognition of particular smells

• Taste (gustation)– Receptor cells (taste buds) respond to four basic

stimulus qualities: sweet, sour, salty, and bitter

• Smell (olfaction)– Molecules enter the nasal passages and pass over

olfactory cells (receptor neurons); responses sent to brain, where they are combined for recognition of particular smells

• Taste (gustation)– Receptor cells (taste buds) respond to four basic

stimulus qualities: sweet, sour, salty, and bitter


The Skin SensesThe Skin SensesThe Skin SensesThe Skin Senses

• Skin senses: touch, pressure, temperature, and pain; receptor cells in skin distributed unevenly throughout the body– Gate-control theory of pain

• Skin senses: touch, pressure, temperature, and pain; receptor cells in skin distributed unevenly throughout the body– Gate-control theory of pain


Perceptual OrganizationPerceptual OrganizationPerceptual OrganizationPerceptual Organization

• Learning Outcomes– Explain the gestalt laws of organization– Identify top-down and bottom-up processing– Define perceptual constancy– Explain depth perception– Relate motion perception to daily life– Determine the importance of perceptual illusions

• Learning Outcomes– Explain the gestalt laws of organization– Identify top-down and bottom-up processing– Define perceptual constancy– Explain depth perception– Relate motion perception to daily life– Determine the importance of perceptual illusions


Perceptual OrganizationPerceptual OrganizationPerceptual OrganizationPerceptual Organization

• Figure-ground organization: we usually perceive objects as a figure standing out against a background

• Figure-ground organization: we usually perceive objects as a figure standing out against a background


The Gestalt Laws of OrganizationThe Gestalt Laws of OrganizationThe Gestalt Laws of OrganizationThe Gestalt Laws of Organization

• Principles that describe how we organize pieces of information into meaningful wholes (gestalts = patterns)– Closure– Proximity– Similarity– Simplicity

• Principles that describe how we organize pieces of information into meaningful wholes (gestalts = patterns)– Closure– Proximity– Similarity– Simplicity


Top-Down and Bottom-UpTop-Down and Bottom-UpTop-Down and Bottom-UpTop-Down and Bottom-Up

• Top-down processing: perception is guided by higher-level knowledge, experience, expectations, and motivations

• Bottom-up processing: processing information by progressing from the individual elements of a stimulus and moving up to the perception of the whole

• Top-down processing: perception is guided by higher-level knowledge, experience, expectations, and motivations

• Bottom-up processing: processing information by progressing from the individual elements of a stimulus and moving up to the perception of the whole


Perceptual ConstancyPerceptual ConstancyPerceptual ConstancyPerceptual Constancy

• Physical objects are perceived as unvarying and consistent despite changes in appearance or changes in the physical environment– Ex.: the image on your retina of a person far away

from you is very small, but you understand (perceive) her to be of “normal” size

• Physical objects are perceived as unvarying and consistent despite changes in appearance or changes in the physical environment– Ex.: the image on your retina of a person far away

from you is very small, but you understand (perceive) her to be of “normal” size


Depth PerceptionDepth PerceptionDepth PerceptionDepth Perception

• Depth perception: the ability to view the world in three dimensions and to perceive distance– Binocular disparity

• Depth perception: the ability to view the world in three dimensions and to perceive distance– Binocular disparity


Motion PerceptionMotion PerceptionMotion PerceptionMotion Perception

• How do we perceive motion?– Movement of an object across the retina is perceived

relative to an unmoving background– If a stimulus is coming toward you, the image on the

retina will expand in size, filling more of the visual field, but we assume the stimulus is approaching rather than it’s growing in size

– We factor information about our head and eye movements with information about changes in the retinal image

• How do we perceive motion?– Movement of an object across the retina is perceived

relative to an unmoving background– If a stimulus is coming toward you, the image on the

retina will expand in size, filling more of the visual field, but we assume the stimulus is approaching rather than it’s growing in size

– We factor information about our head and eye movements with information about changes in the retinal image


Perceptual IllusionsPerceptual IllusionsPerceptual IllusionsPerceptual Illusions

• Visual illusions: physical stimuli that consistently produce errors in perception– Muller-Lyer illusion

• Visual illusions: physical stimuli that consistently produce errors in perception– Muller-Lyer illusion

© 2013 the mcgraw-hill companies, inc. all rights reserved. sensation and perception chapter 3

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