Chapter 3: Visual Perception Flashcards
Cornea
Transparent tissue at the front of each eye, plays a key role in focusing incoming light
Lens
Works with cornea, muscles control the degree of curvature of the lens, allowing a sharp image to appear on the retina
Retina
Light-sensitive tissue that lines the back of the eyeball
Photoreceptors
Cells on retina that are sensitive to light and that respond when stimulated by light
Rods
Type of photoreceptors, sensitive to very low light levels but that are unable to discriminate hues and have poor acuity
Cones
Photoreceptors that are able to discriminate hues and have high acuity, concentrated in the retina’s fovea and become less frequent in visual periphery
Acuity
Ability to see fine detail
Fovea
Center of the retina, region of best acuity, looking at an object involves lining it up with the fovea
Bipolar cells
Type of neuron in the eye, receive input from photoreceptors and transmit output to the retinal ganglion cells
Ganglion cells
Type of neuron in the eye, receive input from bipolar cells and the axons of ganglion cells gather to form the optic nerve, carrying info back to LGN
Optic nerve
Bundle of nerve fibers, formed from the ganglion cells, carries info from eyes to brain
Lateral geniculate nucleus LGN
Located in the thalamus, an important 1st stop for visual information traveling into the brain
Lateral inhibition
A pattern in which cells, when stimulated, inhibt the activity of neighboring cells, creating edge enhancement
Edge enhancement
Process created by lateral inhibition in which the neurons give exaggerated responses to edges of surfaces
Mach bands
An illusion in which one perceives a region to be darker or lighter if its adjacent region is lighter or darker
Think about edge enhancement!
Single-cell recording
A technique for recording moment-by-moment activation level of individual neurons
Receptive field
Portion of visual field in which a cell within the visual system responds (fires)
Changes in position and orientation will change firing rate
Center-surround cells
Type of neuron in the visual system that has a “donut shaped” receptive field
Stimulation of the center has a different impact than the “donut”
Area V1
Site on the occipital lobe where axons from the lateral geniculate nucleus first reach the cerebral cortex
This site is the location at which info about the visual world first reaches the brain
Parallel processing
System in which many steps are going on at the same time
Contrast with serial processing
Serial processing
System in which one step happens at a time in succession with others
Contrast with parallel processing
what system
The system of visual circuits and pathways leading from the visual cortex to the temporal lobe and especially involved in object recognition
where system
The system of visual circuits and pathways leading from the visual cortex to the parietal lobe and especially involved in the spatial localization of objects and in coordination of movements
Binding problem
The problem of reuniting various elements of a scene, given that these elements are initally dealt with by different systems in the brain
Neural synchrony
Pattern of neuron firing in which neurons in one brain area fire at the same time as neurons in another
Brain uses this pattern to solve the binding problem
Conjunction errors
Error in perception in which a person correctly perceives what features are present but misperceives how they join together
Necker cube
A classic reversible figure
A 2D drawing that can be perceived as a cube from two different angles
Reversible (or ambiguous) figure
Drawings that can be readily perceived in more than one way
Figure/ground organization
Processing step in which the perceiver determines which aspects of the stimulus belong to the central object and which aspects belong to the background
Gestalt principles
Set of rules that govern how observers organize visual input
Some elements get put together, others are viewed as independent
Visual features
The elements of a visual pattern–lines, curves, etc.
Perceptual constancy
Achievement of perceiving the constant properties of objects in the world despite changes in the sensory info received
Size, shape, brightness
Unconscious inference
Hypothesized steps that perceivers follow in order to take one aspect of the visual scene into account in judging another aspect
Distance cues
Info available to the perceiver that allows the perceiver to judge how far off a target object is
Binocular disparity
A distance cue based on the differences between the two eyes’ views of the world
Difference becomes less pronounces as an object moves further from the person
Monocular distance cues
Features of the visual stimulus that indicate distance even if the stimulus is only viewed by one eye
Pictoral cues
Patterns that can be represented on a flat surface to create the sense of a 3D object or scene
Interposition
Monocular distance cue that relies on the fact that objects farther away are blocked from view by closer objects that happen to be in the viewer’s line of sight
Linear perspective
A cue for distance based on the fact that parallel lines seem to converge as they get farther away from the viewer
Motion parallax
A distance cue based on the fact that as an observer moves, retinal imgaes of nearby objects move more rapidly than those further away
Optic flow
Pattern of change in the retinal image in which the image grows larger as the viewer approaches an object and shrinks as the viewer retreats from it
