sensation the process that occurs when special receptors in
the sense organs are activated, allowing various forms of
outside stimuli to become neural signals in the brain.
transduction the process of converting outside stimuli, such
as light, into neural activity.
just noticeable difference ( jnd or the difference
threshold) the smallest difference between two stimuli that
is detectable 50 percent of the time. Ernest Weber
absolute threshold the lowest level of stimulation that a
person can consciously detect 50 percent of the time the
stimulation is present. Gustav Fechner
habituation tendency of the brain to stop attending to
constant, unchanging information.
sensory adaptation tendency of sensory receptor cells to
become less responsive to a stimulus that is unchanging.
Light enters the eye through the cornea and pupil. The iris
controls the size of the pupil. From the pupil, light passes
through the lens to the retina, where it is transformed into
nerve impulses. The nerve impulses travel to the brain along
the optic nerve.
visual accommodation the change in the thickness of the
lens as the eye focuses on objects that are far away or
close.
cones visual sensory receptors found at the back of the
retina, responsible for color vision and sharpness of vision.
rods visual sensory receptors found at the back of the retina,
responsible for noncolor sensitivity to low levels of light.
blind spot area in the retina where the axons of the three
layers of retinal cells exit the eye to form the optic nerve,
insensitive to light.
dark adaptation the recovery of the eye’s sensitivity to
visual stimuli in darkness after exposure to bright lights.
light adaptation the recovery of the eye’s sensitivity to
visual stimuli in light after exposure to darkness.
trichromatic theory theory of color vision that proposes
three types of cones:red, blue, and green.
afterimages images that occur when a visual sensation
persists for a brief time even after the original stimulus is
removed.
opponent-process theory theory of color vision that proposes
visual neurons (or groups of neurons) are stimulated by light
of one color and inhibited by light of another color.
pinna the visible part of the ear.
auditory canal short tunnel that runs from the pinna to the
eardrum.
cochlea snail-shaped structure of the inner ear that is filled
with fluid.
auditory nerve bundle of axons from the hair cells in the
inner ear.
pitch psychological experience of sound that corresponds to
the frequency of the sound waves; higher frequencies are
perceived as higher pitches.
place theory theory of pitch that states that different pitches
are experienced by the stimulation of hair cells in different
locations on the organ of Corti.
volley principle theory of pitch that states that frequencies
from about 400 Hz to 4000 Hz cause the hair cells (auditory
neurons) to fire in a volley pattern, or take turns in firing.
gustation the sensation of a taste.
Hans Henning 1916, Four Primary Taste
olfaction (olfactory sense) the sensation of smell.
olfactory bulbs areas of the brain located just above the
sinus cavity and just below the frontal lobes that receive
information from the olfactory receptor cells.
somesthetic senses the body senses consisting of the skin
senses, the kinaesthetic sense, and the vestibular senses.
skin senses the sensations of touch, pressure, temperature,
and pain.
kinesthetic sense sense of the location of body parts in
relation to the ground and each other.
vestibular senses the sensations of movement, balance,
and body position.
sensory conflict theory an explanation of motion sickness
in which the information from the eyes conflicts with the
information from the vestibular senses, resulting in dizziness,
nausea, and other physical discomfort.
perception the method by which the sensations experienced
at any given moment are interpreted and organized in some
meaningful fashion.
size constancy the tendency to interpret an object as
always being the same actual size, regardless of its
distance.
shape constancy the tendency to interpret the shape of an
object as being constant, even when its shape changes on
the retina.
brightness constancy the tendency to perceive the
apparent brightness of an object as the same even when the
light conditions change.
figure–ground the tendency to perceive objects, or figures,
as existing on a background.
reversible figures visual illusions in which the figure and
ground can be reversed.
proximity the tendency to perceive objects that are close to
each other as part of the same grouping.
