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Lecture 3: Perceptual &Motor Development (Motor Development (Typical…
Lecture 3: Perceptual &Motor Development
Vision
Visual Acuity
How to Measure
Habituation method ( Violation of Expectation method)
Preferential looking method
Development phases
4 mth-- stripes 0.025 inch thicc
8 mth-- stripes 0.0125
2mth-- stripes 0.05 inch thick
4-5 yrs adult level
Birth-- stripes 0.1 inch thicc (every time divided by 2)
quite poor-->20/600 vision aka vision 30 times poorer than adult
Colour Vision
by 3-4 mth, colour vision same as adults
adults have colour constancy--> recognise its same colour despite diff brightness/even when there's shadow
birth-- poor colour vision but can distinguish stark contrasts eg. red vs grey
Limitations
Getting images of object onto foveas
Focusing response is slow, imprecise
Image focused behind the retina -->hence blurred image
Babies' eyes don't always converge on 1 object
"Reading" images on fovea
Immature cones make it diff for infant to decipher fine lines & colour
infant fovea twice as large as adults, littered with other cells
Perception
Intermodal Perception
Matching sights to sounds(Spelke)
can detect synchrony
bet "Ah or Li" infants look at the face that matches the vowel
Infants look at video that matches the speed of the soundtrack
Bet mum & dad's voice, infant look at face that matches voice
Matching sights & touch(meltzoff & Borton)
Infants look longer at the pacifier that they had previously sucked
Depth Perception
Binocular Cues (4 mths)
eg. as image goes closer, diff bet images each eye sees becomes larger-->perceptual system interprets the disparity as info abt distance
Binocular disparity/parallax: the disparity bet images from left & right eye
Pictorial Cues (7mth)
Relative size
Things in the distance are small
Interposition
occurs when one shape overlaps another, suggesting it must be in front of the other
Linear perspective
parallel lines seem to meet as they extend toward the horizon and converge in distance
Source of depth info from 2D images
Kinetic (dynamic) cues since birth
Motion parallax
Diff ways that near & far objects appear to move relative to motion of the eye
eg. in a moving car, the trees nearby move past faster than the mountain/castle that are far away
Object Perception (Needham et al)
Dissimilar objects condition
infants look longer at move-tgt event cos perceive red & green surfaces to be 2 diff objects
by 4.5 mth infants can use featural info to figure out how many objects are present but cannot do this at 3 mths
Similar objects condition
infants look longer at the move-apart event cos perceive both red blocks as 1 box-->assume similar features mean 1 object
Motor Development
Effects on cognition
understand how their body relates to objects around them
Learn mastery of their own capabilities eg. now i know whether i'm able to complete this task
affects social development eg. can independently move around, choose who to hang out with and interact with others
Reaching video shown in lecture
5mth
can use arms to reach toy, at first only reach straight up front,
After that able to learn how to adjust arms to diff situations eg. reach across opposite side of body
7-8mth
stabilise head & trunk before reaching for toy with arm
only reach for things that are of interest, if not won't bother-->shows object discrimination
learn to keep balance stabilise other body parts while reaching for object
4mth
arms can move in so many diff ways and at 4mth haven't found the muscle pattern to coordinate & direct to toy
feet has more limited range of mvt & easier to control, can reach toy
Reaching Preference Task for 3 cylinders (Newman, atkinson)
8.5-12 mth
Reach for thinnest cylinder cos easiest to grab
12-15mth
Reach randomly cos they know their hands are big enough
5-8.5mth
Reach randomly cos dk their own capabilities yet
Typical development of reaching milestones
7mths: Reaching becomes stable, smooth motion to target
10 mths: Reaching affected by intention
3-4 mths: Grasp objects placed in reach
Variability
Infants achieve milestones at diff times
Infants may go through milestones in diff orders
2-3 mth: Swipe at objects
Gap-crossing task video in lecture
what babies learn abt gaps when they are crawling does not transfer to when they are walking
have to learn the same thing all over again even when the parameters changed slightly
Evidence for depth perception
Yonas' trapezoid
7mth old reached larger side of window while 5 mth old reached at random
7 mth old relied on
relative size
of pictorial cues to perceive distance (larger objects tend to be nearer
5mth old & 7 mth old shown trapezoidal window with one eye covered (prevent use of binocular cues)
showed infants are able to use pictorial cues by 7 mth old but not when 5 mth old
Visual Cliff (campos et al)
conclusion
Infants have to learn the implications of depth by falling
inexperienced crawlers have depth perception but no fear of heights
Experienced 9mth crawlers didn't cross deep side but beginning 7mth crawlers crossed deep side
social referencing
12 inch drop
when ambiguous situation, uncertain what to do, when mum shows fear/joy--> don't cross/cross
40 inch drop
ignore social referencing, refuse to cross regardless of mum
4 inch drop
ignore social referencing, cross even if mum shows fear
infants rely on dynamic/kinetic cues more than pictorial cues for depth perception (TB pg 90)
Strengths of infant vision
Visual recognition (Fagan)
familiarised with 2 identical faces side by side for 2 min then trials, familiar face was paired with novel face
always looked at novel face and capable of long term visual recognition even when tested after 2 days, 1 week or 2 weeks
5-6 mth olds shown B&W pics of faces
Perceptual categorisation (Quinn et al)
familiarised with cats/dogs then during trials, Novel cat was paired with novel dog
if familiarised with cats/dogs-->look longer at dogs/cats (shows good at perceptual categorisation and it's innate)
4 mth olds tested with novelty preference method