the minimum stimulus intensity that an organism can detect
Just Noticeable Difference
the smallest difference in stimulus intensity that a specific sense can detect (shades of paint)
Signal detection theory
the detection of stimuli involves decision processes as well as sensory processes- Which are both influenced by a variety of factors besides stimulus intensity.
Hit
detecting signals when they are present
miss
detecting signals when they are not present
correct rejection
not detecting signals when they are absent
false alarm
detecting signals when they are not present
subliminal perception
the registration of sensory input without conscious awareness- subliminal messages
Sensory adaptation
A gradual decline in sensitivity to prolonged stimulation- smell of pot smoke starts to fade
Built in process that keeps people tuned in to the changes rather than the constants
Light
a form of electromagnetic radiation that travels as a wave- moving at the speed of light
Amplitude(height)- brightness wavelength(distance between peaks)- color
Retina
The neural tissue lining the inside back surface of the eye; it absorbs light, processes images, and sends visual information to the brain.
Cornea
Transparent "window" at the front
Iris
controls amount of light reaching the retina
Pupil
the opening in the center of the iris that permits light to pass into the rear chamber of the eye
Bright Light- Constrict
Dim Light- Dilate
Lens
the transparent eye structure that focuses the light rays falling on the retina
Nearsightedness
close objects are seen clearly but distant objects appear blurry- Light from distant objects focuses in front of the retina
eyeball to long
Farsightedness
A vision deciency in which distant objects are seen clearly but close objects appear blurry- Light from close objects focuses behind the retina.
eyeball to short
Cones
Specialized visual receptors that play a key role in daylight vision and color vision- concentrated most heavily in the retina
Fovea
tiny spot in the center of the retina that contains only cones; visual activity is greatest at this spot. (when you want to see something sharply, centered on the fovea)
Rods
Specialized visual receptors that play a key role in night vision and peripheral vision- greatly outnumber cones in the periphery of the retina
density of rods greatest just outside the fovea
Dark adaptation
process in which the eyes become more sensitive to light in low illumination
Light adaptation
Process whereby the eyes become less sensitive to light in high illumination
Optic disk
A hole in the retina where the optic nerve fibers exit the eye (known as the blindspot)
Lateral antagonism
Occurs when neural activity in a cell opposes activity in surrounding cells (allows the retina to compare the light falling in a specific area against general lighting.
Receptive field- vision
the retinal are that, when stimulated, affects the firing of that cell.
Optic Chiasm
the point at which the optic nerves from the inside half of each eye cross over and then project to the opposite half of the brain.
Dorsal stream (the where pathway)
Processes information about motion and depth- moves on to areas of parietal lobe.
Ventral stream (the what pathway)
Processes information about color and form- moves on to areas of temporal lobe
Trichromatic theory of color vision
The human eye has three types of receptors with differing sensitivities.
Color Blindness
Only have two types of color receptors instead of three
Complementary colors
Colors that produce gray tones when mixed together.
Short wavelength cones
Blue
Medium wavelength cones
Green
Long wavelength cones
Red
Perceptual set
A readiness to perceive a stimulus in a particular way (creates a slant in how someone interprets sensory input)
Inattentional blindness
Failure to see visible objects or events because one's attention is focused elsewhere.
Bottom up processing
A progression from individual elements to the whole
Top down processing
a progression from the whole to the individual elements
Subjective contours
involves the perception of contours where none actually exist
Phi Phenomenon
The illusion of movement created by presenting visual stimuli in rapid succession (like a movie or cartoon)
Figure and ground
Figure is the thing being looked at- ground is the background against which it stands
Proximity
Things that are near one another seem to belong together
Closure
You may complete figures that actually have gaps in them
Similarity
People tend to group stimuli that are similar.
Simplicity
Most general principle of Gestalts- Idea that people tend to group elements that combine to form a "good figure".
Continuity
The principle reflects peoples tendency to follow whatever direction they've been led.