Chapter 5: Sensation and Perception
Sensation
detection of physical energy emitted/reflected in the external environment STIMULATES RECEPTORS in sensory organs
stimulus activates sense receptors
sense receptors are specialized to detect and respond to one type of stimulation (light, smell, taste)
transduction: receptors receive sensory info --> convert energy into neural impulses
neural impulses --> brain via neurons
perception: brain interprets sensory stimuli
Vision
color: WAVELENGTH
brightness: AMPLITUDE
saturation: LIGHT COMPLEXITY
Color vision
trichromatic theory: any color can be created by varying intensities of 3 lights: red, green blue
retina must have 3 different types of color photoreceptors
Opponent-process theory: 3 opposing channels, NOT COLORS
blue-yellow
red-green
black-white (brightness)
Structure of the eye
cornea: transparent protective structure at the front of the eye
pupil: opening in the iris, regulates amount of light
lens: flexible, transparent structure that focuses light
retina: sensory membrane lining inner surface at back of eye
Photoreceception
rods: see black and white
cones: see color
light enters eye & activates photoreceptors
activates bipolar cells
information is sent to visual cortex via thalamus
Sound
Structure of ear
sound waves
tympanic membrane vibrates
vibrations are amplified across ossicles
vibrations against oval window set up standing wave in fluid of vestibuli
pressure bends the membrane, cause hair cells in basilar membrane to vibrate
Touch
Skin
epidermis
protects skin from pathogens
regulates water release
dermis
cushions body
contains receptors
blood vessels
connective tissue
hypodermis
fat storage
blood vessels
connective tissue
Receptors
Merkel
Ruffini
Meissner's corpuscles
Pacinian corpuscles
fast, small
large, slow
small, slow
large, fast
Smell (olfactory cortex)
Gustation (taste)
Mixed sensations
Synesthesia: one sense induces experience in ANOTHER sense
Phantom limb: sensations in amputated arm/leg
Adaptation examples
darkened movie theater
swimming pool on a hot day
smells in a kitchen during cooking
Perceptual systems
Perception: process by which we SELECT, ORGANIZE, and INTERPRET sensory information
Bottom-up processing: based on PHYSICAL FEATURES of stimulus
Top-down processing: how KNOWLEDGE, EXPECTATIONS, PAST EXPERIENCES shape interpretation of sensory info
Perceptual constancies
lightness constancy: perceive lightness of a surface as unchanging, even when the intensity of the incident light is changing at a point or is variable across the surface
color constancy: perceive objects as retaining their color even though lighting conditions may alter their appearance
size constancy: perceive objects to be the same size even when viewed from different distances
shape constancy: perceive objects as maintaining their shape, even if we look at them from different angles so the shape of their image on the retina changes dramatically
Motion perception: change of position relative to other objects
Apparent movements
autokinetic effect: perceive a stationary point of light as moving in a dark room because of tiny eye movements
phi phenomenon: lights flashed very quickly are perceived as motion (WHAT MAKES MOTION PICTURES POSSIBLE)
lateral inhibition: capacity of a neuron to reduce the activity of its neighbors
Gestalt principles: organisms perceive entire patterns/configurations
Good figure: objects grouped together
proximity: close to each other
similarity
continuation: when there's an intersection between 2+ objects
closure
symmetry
Measuring our percepts
psychophysics: relationship between physical characteristics of a stimulus and our psychological experience
Absolute threshold: minimum amount of stimulus energy that an individual can consciously detect 50% of the time
Weber's law: amount of change needed for an individual to RECOGNIZE a change has occurred
the larger/stronger the stimulus, the larger/stronger change required
There is no such thing as perfect threshold because environment is uncertain
single detection theory: quantifies response of an observer to the presentation of a signal in the presence of uncertainty
sensitivity: level of difficulty in detecting that a target stimulus is present
bias: extent to which 1 response is more probable than another
Vocabulary
absolute threshold: minimum intensity of stimulation that must occur before you experience a sensation
difference threshold: minimum amount of change required for a person to detect a difference between two stimuli
fovea: where cones are densely packed
vestibular sense: perception of balance
temporal coding: for encoding low-frequency auditory stimuli — firing rates of cochlear hair cells match the frequency of the sound wave
place coding: for encoding high frequency auditory stimuli, frequency of sound wave is encoded by the location of the hair cells along the basilar membrane
olfactory epithelium: contains receptors for smell
haptic sense: sense of touch
kinesthetic sense: perception of the positions in space and movements of our bodies and limbs