chapter 7

Question 1

what kind of depth perception coverage do humans have compared to other species?

Answer 1

180 degree coverage with a big overlap between both eyes vs 360 degree coverage with no overlap between both eyes

Question 2

what is the overlap in human vision good for?

Answer 2

depth perception

Question 3

convergence

Answer 3

a broad class of eye movements related to how ‘crossed’ your eyes are

the eyes move inward towards each other

Question 4

divergence

Answer 4

the eyes move outward away from each other

Question 5

retinal image

Answer 5

upside down and backwards

Question 6

binocular disparity

Answer 6

the retinal image is slightly different for each eye

Question 7

what happens to an object that lies on the horopter?

Answer 7

it will have zero disparity and fall on corresponding retinal points

Question 8

what happens to an object not on the horopter?

Answer 8

it will have zero disparity and will have different retinal images

Question 9

diplopia

Answer 9

double vision

Question 10

panum’s fusional zone

Answer 10

a small zone around the horopter where the two retinal images are fused (no disparity)

Question 11

stereoscopes

Answer 11

A device that presents two images with slight disparity to give the illusion of stereopsis. First introduced in the 1830s by Sir Charles Whetstone. Common place attraction in Nickelodeon, but eventually viewers were made for home use 1850-1920

Question 12

free fusion

Answer 12

The technique of crossing your eyes to view a stereogram without a stereoscope

Question 13

anaglyph

Answer 13

A stereoscopic photograph with the two images, superimposed, and printed in different colors. When viewed through glasses, that act as color filters, there is an illusory sense of depth

Question 14

Color filtering

Answer 14

Stereoscopes are a device that present a different image to each eye

Question 15

What does stereopsis pose?

Answer 15

Poses a major computational challenge for the visual system.

Question 16

proximity principle/cue

Answer 16

Neighboring objects in the real world, will tend to be close in the retinal images

Question 17

stereoblindness

Answer 17

3 to 5% of the population does not have stereopsis. This is typically due to some childhood eye disorder, such as strabismus

Question 18

Stereo blind patients

Answer 18

These individuals cannot perceive depth, making simple activities like riding a bike or playing catch difficult. These individuals can still use monocular depth cues to estimate depth. only binocular depth perception is affected.

Question 19

How is strabismus fixed?

Answer 19

Infants learn to suppress input from the affected eye. Correcting the eye with surgery later in life will usually not fix the binocular depth perception issues.

Question 20

stereogram

Answer 20

can be used to give the illusion of depth in the 2-D images

Question 21

stereopsis

Answer 21

sensation of depth that results from the binocular disparity between both eyes

Question 22

steroblindness

Answer 22

a relatively common visual disorder where patients do not have binocular depth perception

Question 23

selectivity

Answer 23

At a given moment awareness encompasses only a small subset of the available sensory information

Question 24

Capacity

Answer 24

We can only perform one mental operation at a time. We have a limited mental “resource “to allocate our tasks at hand

Question 25

Attention

Answer 25

A broad class of selective processes in the brain

Question 26

saccades

Answer 26

Very quick and jerky eye movements. Occur about 2 to 3 times per second when you scan a visual scene. They can be measured with an eye tracker. 1/5th of a second, we generate 150,000 per day

Question 27

fixations

Answer 27

focusing the ‘mind’s eye’

Question 28

why are saccades useful?

Answer 28

They allow you to take advantage of enhanced processing at the fovea

Question 29

Do all shifts a visual attention, involve eye movements?

Answer 29

No

Question 30

attentional focus

Answer 30

Invisible to outside observers. Faster than eye movements, 1/10 of a second. Compared to a spotlight.

Question 31

Posner’s Spatial Cueing Task

Answer 31

participants are presented with a central fixation point and peripheral locations where stimuli can appear. a cue is presented to indicate the likely location of a subsequent target stimulus. Participants must then respond to the appearance of the target as quickly and accurately as possible. By manipulating the validity of the cue (valid, invalid, or neutral), researchers can investigate how attention is directed to different spatial locations and how it influences reaction times to target stimuli.

Question 32

What is the result of Posner’s test?

Answer 32

Participants were faster to respond when the cube pointed toward the target than when it pointed away from the target

Question 33

covert orienting

Answer 33

cueing effect occurred when participants weren’t allowed to make eye movements

Question 34

covert shift

Answer 34

refers to the movement of attention from one location to another without any corresponding movement of the eyes or body

Question 35

EEG

Answer 35

Several electrodes are placed on the scalp, they measure electrical activity from populations of neurons in the brain. The electrodes measure brainwaves

Question 36

Visual cortex represents contralateral hemifield

Answer 36

Left V1 represents the right visual hemifield, right V1 represents the left visual hemifield

Question 37

Negative attention

Answer 37

A negativity that appears over visual cortex contralateral to the attended item

Question 38

Left target trials

Answer 38

Right electrodes (target hemifield) are more negative going than left electrodes

Question 39

Right target trials

Answer 39

Left electrodes are more negative going than right electrodes

Question 40

N2PC

Answer 40

Limited in that it can only track whether attention is allocated to one HEMIFIELD

Question 41

how is selective attention controlled in the brain?

Answer 41

Frontal eye fields and posterior parietal cortex

Question 42

Unilateral visual neglect

Answer 42

Patients that have a lesion to posterior parietal cortex, develop severe attentional problems in the contralesional field. They can still see in the effected visual field, but cannot allocate visual attention.