Visual Perception

Question 1

In what order do the eyes receive light?

Answer 1

Light → cornea → lens → retina

Question 2

What are the two kinds of photoreceptors present in the retina?

Answer 2

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

Question 3

What is the path of light after reaching the retina?

Answer 3

Retina → bipolar cells → ganglion cells → optic nerve → lateral geniculate nucleus (LGN) → occipital lobe

Question 4

What is lateral inhibition?

Answer 4

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)

Question 5

What is edge enhancement?

Answer 5

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

Question 6

How is the Mach bands illusion related to edge enhancement?

Answer 6

The enhancement of the edges between each band make the next band to the right appear lighter, creating an artificial gradient

Question 7

Why do researchers create single-cell recordings?

Answer 7

Each cell in the visual cortex has its own receptive field, the neuron firing rates depend on the stimulus presented

Question 8

What are the different kinds of receptive fields?

Answer 8

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

Question 9

How is Area V1 involved with parallel processing?

Answer 9

Area V1 spreads to the parietal cortex and the inferotemporal cortex, with some info getting sent back to V1 to enhance processing

Question 10

What is the difference between serial processing and parallel processing?

Answer 10

Parallel processing has multiple stages of analysis occurring at once, while serial processing has one stage occurring at a time

Question 11

What is involved in the “what” system?

Answer 11

The pathway connecting the occipital lobe and the inferotemporal cortex (aids in the identification of visual objects)

Question 12

What is involved in the “where” system?

Answer 12

The pathway connecting the occipital lobe and the posterior parietal cortex (aids in perception of an object’s location)

Question 13

What is the binding problem?

Answer 13

The task of reuniting elements of a stimulus that were addressed by different systems in different brain regions

Question 14

What helps solve the binding problem?

Answer 14

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

Question 15

What issue can a lack of attention cause?

Answer 15

Conjunction errors - make mistakes about how features are bound/conjoined together

Question 16

What do Gestalt psychologists say about form perception?

Answer 16

The perceptual whole is often different than the sum of its parts - displayed by Necker cube, Kanizsa triangle, etc. (reversible/ambiguous figures)

Question 17

What does it mean when a drawing is “neutral to figure/ground organization”?

Answer 17

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)

Question 18

What are the Gestalt principles?

Answer 18

Similarity
Proximity
Good continuation
Closure
Simplicity

Question 19

Perception involves multiple activities going on in parallel:

Answer 19

Information gathering
Interpretation

Question 20

What is constancy?

Answer 20

Object properties being perceived in a constant manner despite attributes changing when viewing circumstances change (brightness constancy, size constancy, shape constancy, etc.)

Question 21

What is unconscious inference?

Answer 21

Constancy is partially influenced by relationships within the retinal image (relationships between objects stays the same regardless of viewing distance)

Question 22

What demonstrates the role of interpretation in perception?

Answer 22

Illusions (misinterpretations)

Question 23

Why is the perception of depth important?

Answer 23

Need to know distance to make size judgments

Question 24

What are the monocular cues that influence the perception of depth?

Answer 24

Lens adjustment
Pictorial cues (i.e. interposition)
Linear perspective
Texture gradients

Question 25

What is the binocular cue that influences the perception of depth?

Answer 25

Binocular disparity - the difference between each eye’s view of a stimulus (can lead to perception of depth even in absence of other cues)

Question 26

How do we perceive depth through motion?

Answer 26

Motion parallax (further back = move slowly, closer = move quickly)
Optic flow (outer edges = move quickly, central = move slowly)

Question 27

What is the role of redundancy in perceiving depth?

Answer 27

Different cues become more/less important based on circumstances (i.e. binocular disparity is only informative when objects are close to the viewer)