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Myers’ EXPLORING PSYCHOLOGY (4th Ed)
Chapter 4
Sensation and Perception
James A. McCubbin, PhDClemson University
Worth Publishers
SensationSensation
a process by which our sensory receptors and nervous system receive and represent stimulus energy
Perception a process of organizing and interpreting
sensory information, enabling us to recognize meaningful objects and events
SensationBottom-Up Processing
analysis that begins with the sense receptors and works up to the brain’s integration of sensory information
Top-Down Processing information processing guided by higher-
level mental processes as when we construct perceptions drawing
on our experience and expectations
Sensation- Basic Principles
Psychophysics study of the relationship between
physical characteristics of stimuli and our psychological experience of them
Absolute Threshold minimum stimulation needed to detect a
particular stimulus usually defined as the stimulus needed
for detection 50% of the time
Sensation- Thresholds
Subliminal below one’s absolute threshold for
conscious awarenessDifference Threshold
the minimum difference that a person can detect between two stimuli 50 percent of the time
we experience the difference threshold as a just noticeable difference (jnd)
Sensation- Thresholds
When stimuli are detectable less than 50% of the time (below one’s absolute threshold) they are “subliminal”
0
25
50
75
100
Low Absolutethreshold
Medium
Intensity of stimulus
Percentageof correctdetections
Subliminal stimuli
Sensation- Thresholds
Weber’s Law for a difference to be perceived, two
stimuli must differ by a constant minimum percentage
Sensory adaptation diminished sensitivity as a
consequence of constant stimulation
VisionWavelength
the distance from the peak of one wave to the peak of the next
Hue dimension of color determined by
wavelength of lightIntensity
amount of energy in a wave determined by amplitude
VisionAccommodation
the process by which the eye’s lens changes shape to focus the image of objects on the retina
Retina the light sensitive inner surface of eye,
containing the receptor rods and cones plus layers of neurons that begin the processing of visual information
VisionRods
retinal receptors that detect black, white, and gray
necessary for peripheral and twilight visionCones
receptor cells that are concentrated near the center of retina
function in daylight or well-lit conditions detect fine detail and give rise to color
sensation
The Eye
Optic nerve- nerve that carries neural impulses from the eye to the brain
Blind Spot- point at which the optic nerve leaves the eye, creating a “blind spot” because there are no receptor cells located there
Vision- Receptors
Receptors in the Human Eye
Cones Rods
Number
Location in retina
Sensitivity in dim light
Color sensitive? Yes
Low
Center
6 million
No
High
Periphery
120 million
Visual Information Processing
Feature Detectors nerve cells in the
brain that respond to specific features of the stimulusshapeanglemovement
Stimulus
Cell’s responses
Visual Information Processing
Parallel Processing processing several aspects of a
problem simultaneously the brain’s natural mode of
information processing for many functions, including vision
Visual Information Processing
Abstraction:Brain’s higher-level cells respond to combined information from feature-
detector cells
Feature detection:Brain’s detector cells respond to
elementary features-bars, edges, orgradients of light
Retinal processing:Receptor rods and cones
bipolar cells ganglion cells
Recognition:Brain matches the constructed image
with stored images
Scene
Visual Information Processing
Young-Helmholtz Trichromatic (three color) Theory the retina contains three different
retinal color receptors- one most sensitive to red, one to green, and one to blue- which when stimulated in combination can produce the perception of any color
The Three Primary Colors of Light
Color-Deficient Vision
People who suffer red-green blindness have trouble perceiving the number within the design
Visual Information Processing
Opponent-Process Theory theory that opposing retinal processes (red-green,
yellow-blue, white-black) enable color visionsome cells stimulated by green and inhibited by redothers stimulated by red and inhibited by green
Color Constancy perceiving familiar objects as having consistent
color, even if changing illumination alters the wavelengths reflected by the object
Opponent Process- Afterimage Effect
Audition Visual Capture- tendency for vision
to dominate the other senses Audition- the sense of hearing Frequency- the number of complete
wavelengths that pass a point in a given time
Pitch- a tone’s highness or lownessdepends on frequency
Audition- The Ear
Middle Ear the chamber between the
eardrum and cochlea containing three tiny bones (hammer, anvil, stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window
Audition- The EarInner Ear
innermost part of ear, containing the cochlea, semicircular canals and vestibular sacs
Cochlea coiled, bony, fluid-filled tube in the
inner ear through which sound waves trigger nerve impulses
Touch
Skin Sensations pressure
only skin sensation with identifiable receptors
warmth cold pain
PainGate-Control Theory
theory that the spinal cord contains a neurological “gate” that blocks pain signals or allows them to pass on to the brain
“gate” opened by the activity of pain signals traveling up small nerve fibers
“gate” closed by activity in larger fibers or by information coming from the brain
TasteTaste Sensations
sweet sour salty bitter
Sensory Interaction the principle that one sense may influence
another as when the smell of food influences its taste
Body Position and MovementKinesthesis
the system for sensing the position and movement of individual body parts
Vestibular Sense the sense of body movement and
position, including the sense of balance
Perception
Gestalt an organized
whole tendency to
integrate pieces of information into meaningful wholes
Perceptual Organization
Figure and Ground organization of the visual field into objects (figures) that stand out from their surroundings (ground)
Perceptual Organization- GestaltGrouping
the perceptual tendency to organize stimuli into coherent groups
Grouping Principles proximity- group nearby figures together similarity- group figures that are similar continuity- perceive continuous patterns closure- fill in gaps connectedness- spots, lines and areas are seen
as unit when connected
Perceptual Organization- Gestalt
Proximity Similarity
Continuity Closure Connectedness
Perceptual Organization- Gestalt Groupings
Gestalt grouping principles are at work here.
Perceptual Organization-Depth Perception
Depth Perception ability to see objects in three dimensions allows us to judge distance
Binocular cues- depend on use of two eyes retinal disparity
images from the two eyes differ closer the object, the larger the disparity
convergenceneuromuscular cuetwo eyes move inward for near objects
Perceptual Organization-Depth Perception
Monocular Cues-available to either eye alone relative size
smaller image is more distant
interpositioncloser object blocks distant object
relative clarityhazy object seen as more distant
texture coarse --> closefine --> distant
Perceptual Organization-Depth Perception
Visual Cliff
Perceptual Organization-Depth Perception
Relative Size
Perceptual Organization-Depth Perception
Interposition
Perceptual Organization-Depth Perception
Monocular Cues (continued) relative height
higher objects seen as more distant relative motion
closer objects seem to move faster linear perspective
parallel lines converge with distance relative brightness
closer objects appear brighter
Perceptual Organization-Depth Perception
Perspective Techniques
Perceptual Constancy
Perceptual Constancy perceiving objects as unchanging
despite changes in retinal imagecolorshape size
Perceptual Organization
Perceptual Organization-Muller-Lyer Illusion
Perceptual Organization- Size-Distance Relationship
Perceptual Organization-Brightness Contrast
Perceptual InterpretationPerceptual Adaptation
(vision) ability to adjust to an artificially displaced visual fieldprism glasses
Perceptual Set a mental predisposition to perceive one thing and not another
Perceptual Set-Schemas
What you see in the center is influenced by perceptual set
Perceptual Set-Schemas
Flying Saucers or Clouds?
Perception without Sensation?
Extrasensory Perception controversial claim that perception can occur
apart from sensory inputtelepathyclairvoyanceprecognition
Parapsychology the study of paranormal phenomena
ESPpsychokinesis
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