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Perceptual Motor - Lecture 3 (Developmental Psychology) (Basic Vision,…
Perceptual Motor - Lecture 3
(Developmental Psychology)
Basic Vision
Very little vision before birth
Much less mature than others
Limitations
Getting image of object onto fovea
Babies' eyes don't always converge on 1 object
Focusing response is slow, imprecise (image is focused infront of fovea, so blurred images)
Processing image on foveaa
Adult fovea:
Tiny spot, about 50,000 cones
Daylight vision, fine detail, colour
Infant fovea:
Twice as wide, littered with other cells
Cones immature, like stumps
Fovea: Central region of the retina; sharpest vision
Bifoveal Fixation: When we fixate on an object, image of object focused on fovea of each retina
Visual Acuity: The sharpness of vision
Measured by smallest black and white stripes we detect
For infants, prefer stripes to gray patterns, will look at stripe patterns if they can detect them
Infant visual acuity is poor
At birth, the smallest stripes newborns can see are 30 times wider than an adult
20/600 vision
Development of Visual Acuity
Birth - stripes 0.1in from 1 foot away
2 mths - stripes 0.05in thick
4 mths - stripes 0.025in thick
8 mths - stripes 0.0125in thick
4-5 yrs - adult level
Colour Vision: Ability to tell apart different wavelengths of light (called hue)
Poor colour vision:
Infants are better able to tell difference between high contrast colours (e.g. grey vs red, red vs green)
Development of Colour Vision:
1 mth: Grey vs Blue
2 mths: Yellow vs Green
3 mths: Yellow vs Red
Close to adult-like colour vision at 3-4 months
Strengths
Perceptual Categorisation
Detecting similarities among objects
Quinn et al.'s Study
4 mth old tested with novelty preference
Aimed to see if infants can categorise cats and dogs
Method
Familiarisation:
shown 2 colour photos of cats in each trial
6 trials, all different cats
OR
shown 2 colour photos of dogs in each tria
6 trials, all different dogs
Test Trial:
Novel cat paired with a novel dog
Results
familiarised with cat condition, looked longer at novel dog
familiarised with dog condition, looked longer at novel cat
generalisable to other categories
Visual Recognition
Recognising objects after a delay (memory)
Fagan's Study
5-6 mth old
Shown black and white pictures of faces
Method
Familiarisation:
shown 2 identical faces side by side for 2 minutes
Test:
familiar face paired with novel face
delays vary from 10s, 3hrs, 1 day, 1 week, 2 weeks
Results
all groups looked longer at the novel face
similar results with abstract patterns
younger infants also succeed
Capable of long term recognition
Methods in Infant research:
Novelty Preference Method:
(Preferencial Looking Method)
Infants prefer novel stimuli over familiar ones
Pair familiar stimulus with novel
Measure which one they look at longer
If look longer, means that they can tell that it is different
Object Perception
Needham et al.'s study
4.5 mth old using featural information
Violation of expectation method
2 groups (Similar and dissimilar conditions)
Method
(similar condition)
Move-together event:
shown an setup of 2 blocks, one infront of the other but still visible
shown that the back block moves as one unit
Move-apart event:
same setup
shown that the back block moves as separate unit (i.e. only half the block moves
Results
(similar condition)
infants look longer at the move-apart event
assumes similar feature means one object
Method
(dissimilar condition)
Move-together event:
shown setup of 2 blocks, one infront of the other but still visible
half of the back block is oddly shaped (giving the illusion of two objects)
shown that the back block moves as one unit
Move-apart event:
same setup
shown that the back block moves as separate unit (only half the block moves)
Results
(dissimilar condition)
infants look longer at the move-together event
assumes that different features mean more than one object
Intermodal Perception
Ability to integrate information from 2 or more different sensory modalities
A. Auditory-visual integration
Spelke and Owsley Study
3.5 mths old
investigated if infants are able to match the video of the face of either parent to the voice they heard
Kuhl and Meltzoff Study
4 mths old
investigated if infants are able to match the video of the face to the vowel heard
through simple association
infants can detect synchrony (like adults)
Spelke study
4 month old
infants look at video (of either a soft toy bouncing slowly or quickly) that matches the speed of the soundtrack
B. Visual-tactile integration
Meltzoff and Borton Study
1mth old
gave infants to suck either a rigged or smooth pacifier (without seeing the pacifier)
later shown both pacifiers
infants looked longer at the one that they sucked previously
Depth Perception
3 types of cues
A. Binocular cues
Binocular disparity/parallax
: Difference between the images from the left and right eye
Can be used to predict how close the object is to the eyes
Greater disparity = closer object
Stereopsis
Using parallax cues to perceive depth
Involves fusing two images into one image with depth
Convergence
: Relies on the way the two eyes move
Predicts depth by the sensation of muscle strain in the eyes
More strain = closer object
C. Monocular Static/Pictorial Cues
Relative Size
: Things in the distance are small
Interposition
: Close things occlude far things
Linear Perspective
: Lines converge in distance
B. Monocular Kinetic Cues
Motion Parallax
: Apparent speed and direction of objects
Able to perceive depth by speed and direction even with just 1 eye
Looming
: Perception that an expanding object is moving at different rates depending on how close it is
Difference in relative rate of movement allows us to perceive the relative distances of the two objects
Development of Depth Perception
1st. Kinetic Cues - Present at birth
2nd. Binocular Cues - 4 months
3rd. Pictorial Cues - 7 months
Yonas et al.'s Study
5 and 7 mth olds
Method
Baseline condition:
-Normal window, angled to one side
-Both ages reached for the side closest to them
Test condition:
-Trapezoidal window shown straight
-Covered one of infant's eyes
Results
-5mth olds reached at random
-7mth olds reached for the larger side
(7mth olds can use pictorial cues)
Visual Cliff Study (Campos et al.)
Method
2 groups of infants tested with visual cliff
-Experienced crawlers (9mth olds)
-Beginner crawlers (7mth olds)
Results
Experienced:
15/15 crossed the shallow side
0/15 crossed deep side
Beginner:
15/15 crossed shallow side
10/15 crossed deep side
Conclusions
-Inexperienced crawlers have depth perception but no fear of heights
-Infants have to learn the implications of depth
(falls or near falls)
(social referencing)
Social Referencing
4 inch drop:
-ignores social referencing
-infant crosses even if mum shows fear
12 inch drop:
-Infants uncertain of what to do, use social referencing
-if mum shows fear, infants don't cross
-if mum shows joy, infants cross
40 inch drop:
-ignore social referencing
-refuse to cross regardless of mum's emotion
Conclusions
:
-Infants have some depth perception at birth
-All cues present by 7mths
-Have to learn implications of depth (e.g. fear of heights)
Motor Development
Typical Development of reaching milestones
2- 3 months: Swipe at objects
3-4 months: Grasp objects placed in reach
7 months: Reaching becomes stable, smooth motion to target
10 months: Reaching affected by intention
Variability
Infants achieve milestones at different times (no long-term effects on abilities)
Infants may go through milestones in different orders (modern crawling trends)
Motor Development and Cognition
Reaching preference task
Compared 5-15 mth infants
Results
5 - 8.5 month old: reach randomly
(don't know their own capabilities)
8.5 - 12 month old: reach for the thinnest one
(know the thinnest is easiest)
12 - 15 month old: reach randomly
(know their hands are big enough)
Gap-crossing task
infants need to learn how to integrate depth information with locomotion
Fear of heights
Understanding width of gaps
Conclusions
There is a lot of variations to motor development
Motor development has cognitive implications
Infants need to learn how their body relates to their environment