visual development

Question 1

what is visual acuity?

Answer 1

sharpness of visual discrimination

Question 2

how is visual acuity assessed in infants?

Answer 2

• preferential looking paradigm
• study using grey paddle + succession of paddles with increasingly narrow stripes and narrower gaps between the stripes until infants can no longer distinguish between striped paddle and solid grey one

Question 3

what is the timeline for visual acuity in infants?

Answer 3

• at birth: poor visual acuity due to immature cone cells
• 8 months: babies achieve adult-like visual acuity

Question 4

what is the timeline for colour perception?

Answer 4

• birth: infants see in grey scale
• 2 months: colour vision appears; can see red first
• 5 months: adult-like colour perception due to maturity of cones and visual cortex; can discriminate between colour categories and between hues of the same colour

Question 5

how is colour perception tested in infants?

Answer 5

• habituation paradigm
• after being familiarized with one colour or hue, do they look longer at the novel colour/hue?

Question 6

what is the timeline for visual scanning in infants?

Answer 6

• birth: infants scan their visual environment and pause to look at things, but eye movement is jerky so it’s hard to track moving stimuli
• 4 months: able to smoothly track moving objects if moving slowly
• 8 months: adult-like visual scanning due to brain maturation

Question 7

what are the two hypotheses about why infants prefer to look at faces?

Answer 7

1. fusiform face area: located in the temporal lobe next to the lateral occipital complex; specialized to perceive faces
2. infants prefer top-heavy stimuli (tested using preferential looking paradigm)

Question 8

how long does it take for an infant to prefer their mother’s face over the faces of other women?

Answer 8

just a few days after birth

Question 9

what does it mean when we say that infants become “face specialists”? how long does this process take? why does it occur?

Answer 9

• over the first year of their life, infants become better at distinguishing between faces that are frequently experienced in their environment
• 9 months onward: can distinguish between 2 human faces but struggle to distinguish between 2 monkey faces (specialist)
• 6 months: equally good at distinguishing between human and monkey faces (generalist)
• result of perceptual narrowing to improve the ability to perceive stimuli that are encountered often, resulting from synaptic pruning

Question 10

what is synaptogenesis? what is its opposite?

Answer 10

• synaptogenesis: formation of synapses between neurons; rapid right after birth, results in hyperconnectivity in the brain
• opposite of synaptic pruning: elimination of synapses to increase the efficiency of neural communication (results in perceptual narrowing)

Question 11

what is the “other race effect”? why does it occur? what is its timeline in infants?

Answer 11

• people find it easier to distinguish between faces of individuals from their own racial group than between faces from other racial groups
• 3 month olds don’t demonstrate this effect, since they are face generalists
• 9 month olds do demonstrate it, since they are face specialists

Question 12

how does ASD affect face perception?

Answer 12

toddlers with ASD often have difficulty with face perception, as they prefer to look at geometric shapes over pictures of people

Question 13

what is perceptual constancy?

Answer 13

• the perception of objects as being constant in size, shape, colour, etc despite physical differences in the retinal image of the objects
• unconscious automatic process

Question 14

when does perceptual constancy occur in infants? how is this tested?

Answer 14

• habituation paradigm tests perceptual constancy by repeatedly showing a small cube from different distances, then introducing a new larger cube further away to see if the infant can discriminate between the two
• suggests that perceptual constancy is present from birth

Question 15

what is object segregation?

Answer 15

• the ability to identify that objects are separate from each other
• movement is an important cue

Question 16

when does object segregation occur in infants? how is it tested?

Answer 16

• habituation paradigm is used, showing infants a repeated video of a rod moving side to side behind a box, then introduced to one rod vs a broken rod moving side to side
• 4 month olds preferred looking at the broken rod (novel), indicating that they understood the rod behind the box to be a singular object
• newborns were not able to discriminate between the two stimuli, indicating that they do not possess object segregation abilities (learned with experience)

Question 17

what is binocular disparity? when is it perceived in infants?

Answer 17

• difference between the retinal image of an object in each eye that results in two slightly different signals being sent to the brain. the visual cortex then combines the differing neural signals to see one complete image
• important basis for depth perception
• perceived at 4 months old

Question 18

what is a sensitive period? what is the sensitive period for binocular vision?

Answer 18

• a sensitive period is a time during which experience shapes the development of an ability more than at other times
• sensitive period for binocular vision is from birth to age 3. if they do not receive normal visual input until age 3 they may have life-long difficulties with depth perception

Question 19

what are monocular depth cues? when are they perceived? how are they tested?

Answer 19

• depth cues perceived with one eye, such as relative size or overlap
• perceived at 6-7 months
• tested using visual cliff study: 6 month olds will not crawl over the visual cliff but younger children will

Question 20

summarize the entire visual development timeline

Answer 20

• birth: rudimentary visual scanning, poor acuity, greyscale vision, preference for high contrast and faces, perceptual constancy
• 2 months: colour vision appears
• 4 months: object segregation and binocular depth perception
• 5 months: adult-like colour perception
• 6 months: face generalists, monocular depth perception appears
• 8 months: adult like visual scanning and visual acuity
• 9 months: face specialists through perceptual narrowing

Question 21

what aspects of visual development are innate?

Answer 21

• perceptual constancy
• preference for top-heavy stimuli

Question 22

what aspects of visual development improve with brain maturation?

Answer 22

• visual acuity
• colour perception
• visual scanning

Question 23

what aspects of visual development are improved through experience?

Answer 23

• object segregation
• face perception
• depth perception

Question 24

what is intermodal perception?

Answer 24

• the coordinated perception of a singular object/event through two or more sensory systems
• infants can integrate both visual and auditory and visual and motor information early on in development