PSYC*2650 Chapter 3: Visual Perception Flashcards
What is akinetopsia
A disorder causing disruption of movement perception, with other aspects of perception still intact
T or F: Much of what people perceive is distorted and missing information.
True
In what order does light travel through the eye?
- Light hits the surface of the eyeball
- Passes through the cornea and lens
- Then hits the retina
What is the cornea?
The transparent tissue at the front of each eye
What role do the cornea and lens work together to perform?
Work together to focus incoming light
What is the lens?
The transparent tissue located at near the front of each eye
When muscles tighten, the lens bulges, creating the proper shape for focusing on ________ objects.
Nearby
When muscles relax, the lens flattens, creating the proper shape for focusing on ________ objects.
Farther
What is the role of the iris?
Opens and closes to control the amount of light that reaches the retina
What is the retina?
Light-sensitive tissue that lines the back of the eyeball
What are the three layers that make up the retina?
- Photoreceptors
- Bipolar cells
- Ganglion cells
What is the fovea?
The centre of the retina
Which region of the eye has the best acuity?
The fovea
Does the fovea contain more cones or rods?
Cones
T or F: The centre of the fovea has some rods, but not many.
False. The centre of the fovea has no rods.
What are photoreceptors?
Specialized neural cells that respond directly to incoming light
What are the two types of photoreceptors?
- Rods
- Cones
Which type of photoreceptor is more sensitive to light?
Rods
Which type of photoreceptor is unable to discriminate hues?
Rods
Which type of photoreceptor has relatively poor acuity?
Rods
Which type of photoreceptor needs more light to operate?
Cones
Which type of photoreceptor is able to discriminate hues?
Cones
Which type of photoreceptor has a high acuity?
Cones
How do cones detect colour?
There are three types of cones, each having their own pattern of sensitivities to different wavelengths produced by different colours
Where are bipolar cells located?
The middle layer of the retina
Where do bipolar cells receive their input from?
Photoreceptors
Where do bipolar cells transmit their output?
To the retinal ganglion cells
Where are ganglion cells located?
The front-most layer of the retina
What is the structure of the optic nerve?
A bundle of nerve fibres formed by the axons of ganglion cells
Where does the optic nerve carry information?
The lateral geniculate nucleus
What is the lateral geniculate nucleus?
A way station in the thalamus
Where does the lateral geniculate nucleus transmit information?
The primary visual projection area in the occipital lobe
What is area V1?
A site on the occipital lobe where axons from the lateral geniculate nucleus first reach the brain
What is single-cell recording?
Technique for recording moment-by-moment activation level of an individual neuron within a healthy brain
When measuring the activity of a single neuron, what are investigators interested in?
The cell’s firing rate
What unit of measurement is used to describe a cell’s firing rate?
Spikes per second
What is lateral inhibition?
A pattern in which cells, when stimulated, inhibit the activity of neighbouring cells
Which two types of cells in the retina contribute to lateral inhibition?
- Horizontal cells
- Amacrine cells
What does lateral inhibition in the optic nerve facilitate?
Perception of edges/edge enhancement
What is edge enhancement?
A process in which neurons in the visual system give exaggerated responses to the edges of surfaces
What are mach bands?
A type of illusion, in which a region is perceived to be slighter darker if adjacent to a bright region and slightly brighter is adjacent to a dark region
What causes the mach band illusion?
Edge enhancement
What are receptive fields?
The portion of the visual field to which a cell within the visual system responds
What must occur in the receptive field of vision to cause a cell’s firing rate change?
The appropriately shaped stimulus must appear in the appropriate position
What happens if a stimulus in the visual receptive field is of the wrong form or in the wrong position?
The cell’s firing rate will not change
Do different receptive fields exist for different specialized neurons?
Yes
What are centre-surround cells?
A type of neuron in the visual system with a doughnut shaped receptive field
What happens when the centre of the receptive field of a centre-surround cell is stimulated?
Neural firing will increase in frequency
What will happen if both the centre and surround of a centre-surround cell are strongly stimulated?
They will fire no more or less than usual
What are edge detectors?
Cells that fire at their maximum rate when a stimulus within the receptive field contains an edge of a particular orientation
Are edge detectors typically located in the primary or secondary visual cortex?
Primary visual cortex
Are movement detectors typically located in the primary or secondary visual cortex?
Secondary visual cortex
What are movement detectors?
Cells that fire at their maximum rate when a stimulus within the receptive field moves in a particular direction
What is parallel processing?
A system in which processing occurs in steps that are occuring simultaneously
T or F: The visual system relies on serial processing?
False. The visual system relies on parallel processing.
What are two advantages of parallel processing?
- Processing can occur rapidly
- Allows for the possibility of mutual influence among multiple systems
What is serial processing?
A system in which processing occurs in a series of steps
What is the “what” system/pathway?
System of visual circuits and pathways leading from the primary visual cortex to the interotemporal cortex
What is the role of the “what” system/pathway?
Object recognition
Damage to which visual system/pathway causes visual agnosia?
The “what” system
What is visual agnosia?
The inability to recognize visually presented objects, but no issues in recognizing visual orientation or reaching
What is the “where” system/pathway?
The system of visual circuits and pathways leading from the primary visual cortex to the posterior parietal cortex
What is the role of the “where” system/pathway?
Spatial localization of objects and coordination of movements
What happens when the “where” system/pathway is damaged?
Patients have no difficulty identifying objects, but are not able to recognize the object’s orientation or reach for it
What is the binding problem?
The problem of reuniting various elements of a scene, given that elements are initially dealt with by different systems in the brain
What are three elements that contribute to solving the binding problem?
- Spacial position
- Neural synchrony
- Attention
How does spatial position help solve the binding problem?
By overlaying the map of the location of individual elements to combine elements that are in the same areas
What is neural synchrony?
A pattern of firing where neurons in one brain area fire at the same time as neurons in another area
How does neural synchrony help solve the binding problem?
If neurons detecting one element are firing in synchrony with those detecting another element, they are registered as belonging to the same object
T or F: Attention supports binding.
True
What is a conjunction error?
An error in perception where a person correctly perceives what features are present but misperceives how they are joined
What are four ways in which people resolve ambiguity in what they are seeing?
- Gestalt principles
- Figure-ground organization
- Perceptual consistency
- Redundancy
What are gestalt principles?
Rules that govern how we organize and group visual input
What was the phrase coined by Jerome Bruner?
“Beyond the information given”
What did gestalt psychologists argue about the organization of stimulus?
“The perceptual whole is greater than/different from the sum of its parts”
What is the gestalt principle of similarity?
We tend to group together elements that resemble each other as part of the same object
What is the gestalt principle of proximity?
We tend to group together elements that are physically close to each other as part of the same object
What is the gestalt principle of good continuation?
We tend to assume lines and contours are continuous rather than jagged and changing directions
What is the gestalt principle of closure?
We tend to perceive figures as being whole and complete rather than incomoplete
What is the gestalt principle of simplicity?
We tend to interpret a form in the simplest way possible
What is figure/ground organization?
The processing step in which the perceiver determines which aspects of the stimulus belong to the central object and which belong to the background
What is perceptual constancy?
The achievement of perceiving the constant properties of objects even though the sensory information we receive about them changes based on viewing circumstances
What is size constancy?
Correctly perceiving size despite changes in retinal image size created by changes in viewing distance
What is shape constancy?
Correctly perceiving shape despite the change in retinal image created by shifts in viewing angle
What is brightness constancy?
Correctly perceiving the brightness of objects despite changes in light reaching the eye from various illumination
What is unconscious inference?
The hypothesized steps followed during perception, in which viewing circumstances are taken into account in a way that enables you to perceive the constant properties of the visual world
What causes illusions?
A misinterpretation of viewing circumstances, leading to a misperception of the visual field
What are distance cues?
Information available to the perceiver that allows them to judge how far off a target is
What is binocular disparity?
A distance cue based on the differences between the eyes’ views of the world
Is binocular disparity more or less pronounced the farther away an object is?
Less pronounced
T or F: Binocular disparity cannot lead to the perception of depth when no other distance cues are present
False
What are monocular cues?
Features of a visual stimulus that indicate distance even if the stimulus is viewed with only one eye
What are pictorial cues?
Patterns that can be represented on a flat surface to create the perception of a 3D object or scene
What relative height?
A monocular/pictorial cue that states that objects touching the ground tend to be further away the higher their position is/the closer they are to the horizon
What is atmospheric perspective?
A monocular/pictorial cue that states that in nature, distant objects tend to be less sharp, and bluer (during the daytime)
What is interposition/occlusion
A monocular distance cue, which states that closer objects will block farther objects if they’re both in the viewer’s line of sight
What is linear perspective?
A monocular distance cue based on the fact that parallel lines seem to converge as they get further from the viewer
What is the motion parallax?
A distance cue based on the fact that as an observer moves, the retinal images of nearby objects move more rapidly than those that are far
What is optic flow?
A pattern of change in the retinal image, in which the object appears to grow larger as the viewer approaches and shrink as they retreat
What feature of visual perception allows distance to be judged in nearly any situation?
Redundancy
What does redundancy allow for when perceiving distance?
Flexibility and versatility
