Visual Perception Flashcards
In what order do the eyes receive light?
Light → cornea → lens → retina
What are the two kinds of photoreceptors present in the retina?
Rods - sensitive to low levels of light, lower acuity, colorblind, not present in the fovea
Cones - cannot function in dim light, higher acuity, color sensitive, and are mostly present in/near the fovea
What is the path of light after reaching the retina?
Retina → bipolar cells → ganglion cells → optic nerve → lateral geniculate nucleus (LGN) → occipital lobe
What is lateral inhibition?
When cells are stimulated, they inhibit the activity of neighboring cells (i.e. a cell will be less inhibited if only one of its neighbors is stimulated instead of both)
What is edge enhancement?
A product of lateral inhibition: cells that signify the edge of a stimulus receive less inhibition than those that signify the middle of a stimulus
How is the Mach bands illusion related to edge enhancement?
The enhancement of the edges between each band make the next band to the right appear lighter, creating an artificial gradient
Why do researchers create single-cell recordings?
Each cell in the visual cortex has its own receptive field, the neuron firing rates depend on the stimulus presented
What are the different kinds of receptive fields?
Center-surround cells - stimulus in the center of the receptive fields leads to faster firing rates
Receptors specialized for orientation - angles, motion and direction (“movement detectors”), corners
How is Area V1 involved with parallel processing?
Area V1 spreads to the parietal cortex and the inferotemporal cortex, with some info getting sent back to V1 to enhance processing
What is the difference between serial processing and parallel processing?
Parallel processing has multiple stages of analysis occurring at once, while serial processing has one stage occurring at a time
What is involved in the “what” system?
The pathway connecting the occipital lobe and the inferotemporal cortex (aids in the identification of visual objects)
What is involved in the “where” system?
The pathway connecting the occipital lobe and the posterior parietal cortex (aids in perception of an object’s location)
What is the binding problem?
The task of reuniting elements of a stimulus that were addressed by different systems in different brain regions
What helps solve the binding problem?
Spatial position - overlay map of “what forms are where”
Neural synchrony - attributes are registered as belonging to the same object if the neurons detecting these attributes fire in synchrony
Attention
What issue can a lack of attention cause?
Conjunction errors - make mistakes about how features are bound/conjoined together
What do Gestalt psychologists say about form perception?
The perceptual whole is often different than the sum of its parts - displayed by Necker cube, Kanizsa triangle, etc. (reversible/ambiguous figures)
What does it mean when a drawing is “neutral to figure/ground organization”?
It can be perceived as either part of the figure or part of the ground (i.e. the Canadian flag perceived as either a leaf or two faces facing each other)
What are the Gestalt principles?
Similarity
Proximity
Good continuation
Closure
Simplicity
Perception involves multiple activities going on in parallel:
Information gathering
Interpretation
What is constancy?
Object properties being perceived in a constant manner despite attributes changing when viewing circumstances change (brightness constancy, size constancy, shape constancy, etc.)
What is unconscious inference?
Constancy is partially influenced by relationships within the retinal image (relationships between objects stays the same regardless of viewing distance)
What demonstrates the role of interpretation in perception?
Illusions (misinterpretations)
Why is the perception of depth important?
Need to know distance to make size judgments
What are the monocular cues that influence the perception of depth?
Lens adjustment
Pictorial cues (i.e. interposition)
Linear perspective
Texture gradients
