general psychology chapter 3 sensation and perception chapter 3 sensation and perception
TRANSCRIPT
General PsychologyGeneral Psychology
Chapter 3
Sensation and Perception
Chapter 3
Sensation and Perception
Sensation and PerceptionSensation and Perception
Sensation – process of detecting external stimuli and changing those stimuli into nervous system activity
Perception – cognitive process that involves the selection, organization, and interpretation of stimuli
Sensation – process of detecting external stimuli and changing those stimuli into nervous system activity
Perception – cognitive process that involves the selection, organization, and interpretation of stimuli
Concepts Related to Sensory Processes
Concepts Related to Sensory Processes
Sensory threshold – minimum intensity of a stimulus that will cause the sense organs to operate
Psychophysics – study of relationships between the physical attributes of stimuli and psychological experiences they produce
Sensory threshold – minimum intensity of a stimulus that will cause the sense organs to operate
Psychophysics – study of relationships between the physical attributes of stimuli and psychological experiences they produce
Figure 3.1: Examples of absolute threshold values for the five senses (i.e., these stimuli will be detected 50 percent of the time).
Figure 3.1: Examples of absolute threshold values for the five senses (i.e., these stimuli will be detected 50 percent of the time).
Concepts Related to Sensory Processes
Concepts Related to Sensory Processes
Absolute threshold – physical intensity of a stimulus that a person reports detecting 50% of the time
Used to see whether a person’s senses are operating properly
Absolute threshold – physical intensity of a stimulus that a person reports detecting 50% of the time
Used to see whether a person’s senses are operating properly
Concepts Related to Sensory Processes
Concepts Related to Sensory Processes
• Signal detection theory – states that stimulus detection is a decision-making process of determining whether a signal exists against a background of noise
• Signal detection theory – states that stimulus detection is a decision-making process of determining whether a signal exists against a background of noise
ThresholdsThresholds
Difference threshold – smallest difference between stimulus attributes that can be detected
Just noticeable difference (jnd) – amount of change in a stimulus that makes it just noticeably different from what it was
Difference threshold – smallest difference between stimulus attributes that can be detected
Just noticeable difference (jnd) – amount of change in a stimulus that makes it just noticeably different from what it was
Sensory AdaptationSensory Adaptation
Occurs when our sensory experience decreases with continued exposure to a stimulus Dark adaptation – process in which the visual
receptors become more sensitive to light as we spend time in the dark
Light adaptation – process by which our eyes become more sensitive to dark when we spend time in the light
Occurs when our sensory experience decreases with continued exposure to a stimulus Dark adaptation – process in which the visual
receptors become more sensitive to light as we spend time in the dark
Light adaptation – process by which our eyes become more sensitive to dark when we spend time in the light
Figure 3.8: The dark adaptation curve. Figure 3.8: The dark adaptation curve.
Light:Stimulus for Vision
Light:Stimulus for Vision
Light – wave of electromagnetic energy Wave amplitude – intensity or brightness of light Wavelength – distance between any point in a wave
and the corresponding point on next cycle (e.g., peak to peak), measured in nanometers (nm)
Determines the color or hue we perceive Wave purity – refers to characteristic of saturation
Light – wave of electromagnetic energy Wave amplitude – intensity or brightness of light Wavelength – distance between any point in a wave
and the corresponding point on next cycle (e.g., peak to peak), measured in nanometers (nm)
Determines the color or hue we perceive Wave purity – refers to characteristic of saturation
Figure 3.2: Representations of light waves differing in wavelength and wave amplitude. Figure 3.2: Representations of light waves differing in wavelength and wave amplitude.
Figure 3.3: The visible spectrum, in which wavelengths of approximately 380-760 nanometers are visible to the human eye and are perceived as various hues.
Figure 3.3: The visible spectrum, in which wavelengths of approximately 380-760 nanometers are visible to the human eye and are perceived as various hues.
Figure 3.4: Relationships between physical characteristics of light and our psychological experience of that light.
Figure 3.4: Relationships between physical characteristics of light and our psychological experience of that light.
Figure 3.5: The major structures of the human eye.Figure 3.5: The major structures of the human eye.
The Eye:Receptor for Vision
The Eye:Receptor for Vision
Cornea – outer shell of eye Protects structures at front of eye First point where light rays are bent
Pupil – opening through which light enters eye Iris – colored part of the eye that expands or
contracts, depending on light intensity Ciliary muscles – expand or contract to change
shape of the lens to bring image into focus (accommodation)
Cornea – outer shell of eye Protects structures at front of eye First point where light rays are bent
Pupil – opening through which light enters eye Iris – colored part of the eye that expands or
contracts, depending on light intensity Ciliary muscles – expand or contract to change
shape of the lens to bring image into focus (accommodation)
Figure 3.6: The major features of the human retina.Figure 3.6: The major features of the human retina.
The Eye:Receptor for Vision
The Eye:Receptor for Vision
The eye is filled with two fluids:1. Aqueous humor – provides nourishment to
the cornea and other structures at the front of the eye
2. Vitreous humor – fills the interior of the eye, behind the lens, where it functions to keep the eyeball spherical
The eye is filled with two fluids:1. Aqueous humor – provides nourishment to
the cornea and other structures at the front of the eye
2. Vitreous humor – fills the interior of the eye, behind the lens, where it functions to keep the eyeball spherical
VisionVision Begins to take place at the retina, where
light energy is transduced to neural energy
Begins to take place at the retina, where light energy is transduced to neural energy
Rods
Photosensitive cells that are most active in low levels of illumination and do not respond differently to different wavelengths of light
Cones
Photosensitive cells that operate best at high levels of illumination and are responsible for color vision
The Eye, Con’t.The Eye, Con’t.
Optic Nerve – formed of fibers from ganglion cells; leaves the eye and starts back toward other parts of the brain
Fovea – small area of retina with the best visual acuity. It is packed with cones cells (no rods!).
Blind spot – where nerve impulses from rods and cones leave the eye
Optic Nerve – formed of fibers from ganglion cells; leaves the eye and starts back toward other parts of the brain
Fovea – small area of retina with the best visual acuity. It is packed with cones cells (no rods!).
Blind spot – where nerve impulses from rods and cones leave the eye
Figure 3.7: This figure provides two ways to locate your blind spot. Figure 3.7: This figure provides two ways to locate your blind spot.
Visual PathwayVisual Pathway
Left visual field – everything off to your left ends up in right occipital lobe
Right visual field – everything off to your right ends up in left occipital lobe
Optic chiasma – sorting of which fibers of the optic nerve get directed where largely occurs here
Left visual field – everything off to your left ends up in right occipital lobe
Right visual field – everything off to your right ends up in left occipital lobe
Optic chiasma – sorting of which fibers of the optic nerve get directed where largely occurs here
Figure 3.9: Cross Laterality.Figure 3.9: Cross Laterality.
Color VisionColor Vision
Trichromatic theory – First proposed by Thomas Young and revised by Herman von Helmholtz The eye contains 3 distinct receptors for color
Each responds best to one of 3 primary colors of light: red, blue, and green
By the careful combination of all 3, all other colors can be produced
Trichromatic theory – First proposed by Thomas Young and revised by Herman von Helmholtz The eye contains 3 distinct receptors for color
Each responds best to one of 3 primary colors of light: red, blue, and green
By the careful combination of all 3, all other colors can be produced
Figure 3.10: The relative sensitivities of three types of cones to lights of differing wavelengths.
Figure 3.10: The relative sensitivities of three types of cones to lights of differing wavelengths.
Color VisionColor Vision Opponent-process theory – Ewald Hering
proposed this theory in 1870 Three pairs of visual mechanisms that respond
to different wavelengths of light Blue-yellow processor Red-green processor Black-white difference/brightness processor
Each is capable of responding to either of the two hues that give it its name, but not both
Opponent-process theory – Ewald Hering proposed this theory in 1870 Three pairs of visual mechanisms that respond
to different wavelengths of light Blue-yellow processor Red-green processor Black-white difference/brightness processor
Each is capable of responding to either of the two hues that give it its name, but not both
Color BlindnessColor Blindness In dichromatism, there is a lack of one type
of cone (supporting Young-Helmholtz’s theory)
However, color vision defects higher in the visual pathway support the opponent-process theory
Both theories are probably correct, each in its own way
In dichromatism, there is a lack of one type of cone (supporting Young-Helmholtz’s theory)
However, color vision defects higher in the visual pathway support the opponent-process theory
Both theories are probably correct, each in its own way
Gender Differences in Perception of Color?
Gender Differences in Perception of Color?
Reliable, stable differences in color preferences:
1. Women prefer “cool colors,” while men prefer bright, strong colors
2. Women are more likely to have a favorite color
3. Women can name more colors
4. Color matters more to women.
Reliable, stable differences in color preferences:
1. Women prefer “cool colors,” while men prefer bright, strong colors
2. Women are more likely to have a favorite color
3. Women can name more colors
4. Color matters more to women.
Sound: Stimulus for Hearing
Sound: Stimulus for Hearing
Sound – series of pressures of air (or some other medium) beating against the ear Amplitude – intensity that determines the
psychological experience we call loudness Zero point on decibel scale (perceived loudness) is
lowest intensity of sound that can be detected – absolute threshold
Sound – series of pressures of air (or some other medium) beating against the ear Amplitude – intensity that determines the
psychological experience we call loudness Zero point on decibel scale (perceived loudness) is
lowest intensity of sound that can be detected – absolute threshold
Figure 3.11: Sound waves are manifested as changes in air pressure are produced as the tines of the tuning fork vibrate back and forth.
Figure 3.11: Sound waves are manifested as changes in air pressure are produced as the tines of the tuning fork vibrate back and forth.
Sound, Con’t.Sound, Con’t. Frequency – number of waves exerted for
every second of Unit of sound is called hertz (Hz) {20-20,000 Hz}
Pitch – how high or low a tone is (determined by wavelength)
Purity – timbre is character of sound that reflects degree of purity
White noise is a random mixture of sound frequencies
Frequency – number of waves exerted for every second of Unit of sound is called hertz (Hz) {20-20,000 Hz}
Pitch – how high or low a tone is (determined by wavelength)
Purity – timbre is character of sound that reflects degree of purity
White noise is a random mixture of sound frequencies
Figure 3.12: Loudness values in decibel units for various sounds.Figure 3.12: Loudness values in decibel units for various sounds.
Figure 3.13: A summary of the ways in which the physical characteristics of light and sound waves affect our psychological experiences of vision and hearing.
Figure 3.13: A summary of the ways in which the physical characteristics of light and sound waves affect our psychological experiences of vision and hearing.
Ear:Receptor for Hearing
Ear:Receptor for Hearing
Cochlea – major structure of inner ear Receptor cells (transducers for hearing) are
here When fluid inside cochlea moves, basiliar
membrane is bent up & down, which stimulates receptors (hair cells)
Neural impulses travel on auditory nerve toward temporal lobe
Cochlea – major structure of inner ear Receptor cells (transducers for hearing) are
here When fluid inside cochlea moves, basiliar
membrane is bent up & down, which stimulates receptors (hair cells)
Neural impulses travel on auditory nerve toward temporal lobe
Figure 3.14: The major structures of the human ear.Figure 3.14: The major structures of the human ear.
Chemical SensesChemical Senses
Taste = gustation Four psychological qualities: sweet, salty, sour,
and bitter Taste buds – receptor cells for taste on tongue We have about 10,000 taste buds
Taste = gustation Four psychological qualities: sweet, salty, sour,
and bitter Taste buds – receptor cells for taste on tongue We have about 10,000 taste buds
Figure 3.15: Enlarged view of a taste bud, the receptor for gustation.Figure 3.15: Enlarged view of a taste bud, the receptor for gustation.
Chemical Sense, Con’t.Chemical Sense, Con’t.
Smell = Olfaction Pheromones – chemicals that many animals
emit that produce distinctive odors that are used as a method of communication between organisms
VNO (vomeronasal organ) – primary organ used in detection of pheromones. Involved in mating, territoriality, and aggressiveness in animals.
Smell = Olfaction Pheromones – chemicals that many animals
emit that produce distinctive odors that are used as a method of communication between organisms
VNO (vomeronasal organ) – primary organ used in detection of pheromones. Involved in mating, territoriality, and aggressiveness in animals.
Figure 3.16: The olfactory system, showing its proximity to the brain and transducers for smell — the hair cells.
Figure 3.16: The olfactory system, showing its proximity to the brain and transducers for smell — the hair cells.
The Skin-Cutaneous SensesThe Skin-Cutaneous Senses A square inch of skin contains nearly 20
million cells Some skin receptor cells have free nerve
endings, while others have encapsulated nerve endings
Our ability to discriminate among types of cutaneous sensation is due to a unique combination of responses the receptor cells have to various types of stimulation
A square inch of skin contains nearly 20 million cells
Some skin receptor cells have free nerve endings, while others have encapsulated nerve endings
Our ability to discriminate among types of cutaneous sensation is due to a unique combination of responses the receptor cells have to various types of stimulation
Figure 3.17: A patch of hairy skin, showing the layers of skin and several nerve cells.Figure 3.17: A patch of hairy skin, showing the layers of skin and several nerve cells.
Figure 3.18: A demonstration that our sense of what is hot can be constructed from sensations of what is warm and cold.
Figure 3.18: A demonstration that our sense of what is hot can be constructed from sensations of what is warm and cold.
Position SensesPosition Senses
Vestibular Sense Tells us about balance,
where we are in relation to gravity and about acceleration or deceleration
Receptors are located on either side of the head, near the inner ear (5 chambers)
Over-stimulation may result in motion sickness
Vestibular Sense Tells us about balance,
where we are in relation to gravity and about acceleration or deceleration
Receptors are located on either side of the head, near the inner ear (5 chambers)
Over-stimulation may result in motion sickness
Kinesthetic sense Tells us about the position of
various parts of our bodies and what our muscles and joints are doing
Receptors are located primarily in our joints, but some information comes from muscles and tendons
Information from these receptors travels via the spinal cord
They provide examples of reflex reactions
Kinesthetic sense Tells us about the position of
various parts of our bodies and what our muscles and joints are doing
Receptors are located primarily in our joints, but some information comes from muscles and tendons
Information from these receptors travels via the spinal cord
They provide examples of reflex reactions
A Special Sense:Pain
A Special Sense:Pain
Theories of pain:1. Gate control mechanism (high in spinal cord)
that opens to let pain messages race to brain or closes to block messages
2. Cognitive behavioral – pain is influenced by attitudes, expectations and behaviors
Theories of pain:1. Gate control mechanism (high in spinal cord)
that opens to let pain messages race to brain or closes to block messages
2. Cognitive behavioral – pain is influenced by attitudes, expectations and behaviors
Pain ManagementPain Management
Drug therapy Hypnosis & cognitive self-control Acupuncture Placebo – a substance a person thinks will
be helpful in treatment Counterirritation – stimulating an area of
the body near the location of the pain
Drug therapy Hypnosis & cognitive self-control Acupuncture Placebo – a substance a person thinks will
be helpful in treatment Counterirritation – stimulating an area of
the body near the location of the pain
Paying Attention: A Process of Selection
Paying Attention: A Process of Selection
Salient detail – one that captures our attention Remembered better than peripheral details
(which are part of the perceptual background) Stimulus factors make some details more
compelling than others Personal factors – characteristics of a
perceiver that influence which stimuli get attended to
Salient detail – one that captures our attention Remembered better than peripheral details
(which are part of the perceptual background) Stimulus factors make some details more
compelling than others Personal factors – characteristics of a
perceiver that influence which stimuli get attended to
Stimulus FactorsStimulus Factors Contrast – extent to which a stimulus is
physically different from the other stimuli around it Most important factor in perceptual selectivity The more intense a stimulus is, the more likely
we are to attend to it Motion is another dimension for which contrast
is important Repetition can also influence attention
Contrast – extent to which a stimulus is physically different from the other stimuli around it Most important factor in perceptual selectivity The more intense a stimulus is, the more likely
we are to attend to it Motion is another dimension for which contrast
is important Repetition can also influence attention
Personal Factors in ProcessingPersonal Factors in Processing Bottom-Up
Processing Attend to a
stimulus, organize and identify it, and then store it in memory
Bottom-Up Processing Attend to a
stimulus, organize and identify it, and then store it in memory
Top-Down Processing Motivation,
mental set, and past experience influence perceptual sensitivity
Top-Down Processing Motivation,
mental set, and past experience influence perceptual sensitivity
Figure 3.19: How we perceive the world is determined at least in part by our mental set, or our expectations about the world.
Figure 3.19: How we perceive the world is determined at least in part by our mental set, or our expectations about the world.
Gestalt PsychologyGestalt Psychology A gestalt forms when one sees the overall
scheme of things: the whole, totality or configuration.
Gestalt Psychology – basic principle is figure-ground relationship Of all the stimuli in your environment, those
you attend to and group together are “figures” All other stimuli become “ground”
A gestalt forms when one sees the overall scheme of things: the whole, totality or configuration.
Gestalt Psychology – basic principle is figure-ground relationship Of all the stimuli in your environment, those
you attend to and group together are “figures” All other stimuli become “ground”
Figure 3.20: (A) A classic reversible figure-ground pattern. Figure 3.20: (A) A classic reversible figure-ground pattern.
Grouping Stimuli with Bottom-Up Processing
Grouping Stimuli with Bottom-Up Processing
Proximity Similarity Continuity Common fate Closure
Proximity Similarity Continuity Common fate Closure
Figure 3.21: Four Gestalt psychology examples of grouping. Figure 3.21: Four Gestalt psychology examples of grouping.
Figure 3.22: An example of subjective contour.Figure 3.22: An example of subjective contour.
Grouping Stimuli with Top-Down Processing
Grouping Stimuli with Top-Down Processing
Perceiving stimuli because we want to, expect to, or have experienced them together in the past
How we ultimately organize our experiences depends on both types of processing
Perceiving stimuli because we want to, expect to, or have experienced them together in the past
How we ultimately organize our experiences depends on both types of processing
Figure 3.23: An example of top-down processing.Figure 3.23: An example of top-down processing.
Perceiving Depth & DistancePerceiving Depth & Distance
Ocular cues are built into our visual system and tell us about depth and distance
Retinal disparity – each eye gets a somewhat different view of a 3-dimensional object
Convergence – eyes turning in, toward each other, when something is viewed up close
Ocular cues are built into our visual system and tell us about depth and distance
Retinal disparity – each eye gets a somewhat different view of a 3-dimensional object
Convergence – eyes turning in, toward each other, when something is viewed up close
Figure 3.24: When looking at a three-dimensional object, such as a pen, the right eye sees a slightly different image than does the left eye — a phenomenon called retinal disparity.
Figure 3.24: When looking at a three-dimensional object, such as a pen, the right eye sees a slightly different image than does the left eye — a phenomenon called retinal disparity.
Monocular CuesMonocular Cues Physical cues to depth and distance are
those we get from the structure of our environment Linear Perspective Interposition Relative Size Texture gradient Patterns of Shading Motion Parallax
Physical cues to depth and distance are those we get from the structure of our environment Linear Perspective Interposition Relative Size Texture gradient Patterns of Shading Motion Parallax
Figure 3.25: At the level of the retina, we experience different images; yet we know we are looking at the same door because of shape constancy.
Figure 3.25: At the level of the retina, we experience different images; yet we know we are looking at the same door because of shape constancy.
Constancy of Visual PerceptionConstancy of Visual Perception
Perceptual constancies help us organize and interpret the stimulus input we get from our senses. They allow us to see stimuli as constant, regardless of changing conditions. Size constancy Shape constancy Brightness constancy Color constancy
Perceptual constancies help us organize and interpret the stimulus input we get from our senses. They allow us to see stimuli as constant, regardless of changing conditions. Size constancy Shape constancy Brightness constancy Color constancy
When Constancy Fails…When Constancy Fails… Illusions – experiences in which our
perceptions are at odds with what we know as physical reality
Illusions remind us that perception is a higher level process than sensation!
Illusions – experiences in which our perceptions are at odds with what we know as physical reality
Illusions remind us that perception is a higher level process than sensation!
Figure 3.26: A few classic geometrical illusions. Figure 3.26: A few classic geometrical illusions.
Figure 3.27: Impossible figures — examples of conflicting visual information.Figure 3.27: Impossible figures — examples of conflicting visual information.
Figure 3.29: Müller-Lyer illusion. Figure 3.29: Müller-Lyer illusion.
Cultural Bias in Perception?Cultural Bias in Perception?
Yes! There is a role of culture in the development of depth perception.
However, with training, most cultural differences in the perception of depth disappear.
Yes! There is a role of culture in the development of depth perception.
However, with training, most cultural differences in the perception of depth disappear.
Figure 3.28: Which animal — the antelope or the elephant — is the hunter about to spear? Figure 3.28: Which animal — the antelope or the elephant — is the hunter about to spear?