Infant Perception
I. Basic Vision
A. Limitations
• Bifoveal fixation: When fixate object, image of
object focused on fovea at center of each retina
-- very little before birth
-- much less mature than other senses
at birth
-- still, both limitations and strengths
• Two kinds of limitations
1. Getting image of object onto foveas
b. Focusing response slow, imprecise
a. Lack of convergence
Eyes don’t always converge on one object!
Images focused in front of foveas!
So blurred images
2. “Reading” image on foveas
a. Poor acuity
Adult fovea:
-- Smallest black and white stripes we detect
-- tiny spot, ≈ 50,000 cones
-- daylight vision, fine detail, color
-- How do we measure infants’ acuity?
Infant fovea:
-- twice as wide, littered with other cells
-- cones immature, like stumps
Infants prefer stripes to grey patterns,
will look at stripes if can detect them
1
• Birth:
Smallest stripes newborn can see 30 times
wider than adult!
Adult: 20/20
Infant: 20/600
• Development:
birth: stripes 1/10” one foot away
2 mos: 1/2 this thick
4 mos: 1/4 this thick
8 mos: 1/8 this thick (≈ weak eyeglasses)
- 5years: Adult level
4
• Development:
1 mo: grey vs blue
2 mos: yellow vs green
3 mos: yellow vs red
By -3 4mos, color vision is basically adult- like
b. Poor color vision
• Birth:
grey vs red
green
yellow
red vs green
B. Strengths
Novelty Preference Method:
Infants prefer novel over familiar stimuli
-- Show stimulus until familiar
-- Pair familiar and novel stimuli
If prefer novel, can distinguish them
2
1. Perceptual categorization
-- Can infants detect similarities among
stimuli?
Quinn et al.
- 4mos
3
Cats vs dogs?
FAMILIARIZATION:
Results:
-- Familiarized with cats, prefer dogs
-- Familiarized with dogs, prefer cats
Familiarization trials:
-- on each trial, two color photos of cats
(or dogs)
-- six trials, all different cats (or dogs)
Test trials:
-- Novel cat and novel dog
TEST:
2. Visual recognition
-- Can infants recognize stimuli after
a delay?
Fagan
Other categories: dogs/birds
horses/giraffes
chairs/couches
etc.
- 6mos
5
Stimuli: faces
(black and white)
• Capable of perceptual categorization
3
Familiarization trial:
-- two identical faces, 2 minutes
FAMILIARIZATION:
Delay:
-- 10 s
-- 3hours
-- 1day
-- 2days
-- 1week
-- 2weeks
Test trials:
-- familiar face and novel face
TEST:
Results:
-- Prefer novel face at all delays!!!
-- Similar results with: abstract patterns
younger infants
• Capable of long- term visual recognition
C. Conclusions
-- Young infants’ visual world initially
lacks in sharpness, detail, color…
II. Depth Perception
A. Adults: 3 classes of cues
Binocular cues:
-- Still, young infants can do a lot with
what they do see: categorize and recognize
visual stimuli
e.g., binocular disparity
differences between left and
right images
4
Monocular kinetic cues:
Monocular static or pictorial cues:
e.g., motion parallax
e.g., linear perspective
direction and speed of
apparent motions
less separation with distance
5
B. Infants
• At what age each cue?
• How do they come to use it?
• How do they recalibrate?
• Evidence:
• Development:
Example: Pictorial cues
birth: kinetic cues
Yonas et al.
4 mos: binocular cues
5, 7 mos
7 mos: pictorial cues
Baseline Condition:
real window, angled left or right
Test Condition:
trapezoidal window, shown frontally
patch on one eye, so no binocular cues
both ages: reach for closer side
6
Results:
7 mos: reach for larger, “closer” side
C. Fear of heights
Visual cliff: deep and shallow sides
5 mos: reach for either side
• Only at 7 mos can use pictorial cues
Campos et al.
2 groups:
-- Experienced crawlers (9 mos)
-- Beginning crawlers (7 mos)
15 per group
Results:
Experienced:
15/15 cross shallow
0/15 cross deep
Beginning:
15/15 cross shallow
10/15 cross deep (most!)
Related results:
-- Babies in harness (Rader et al.)
Conclusions:
-- Inexperienced crawlers have depth
perception, but NO fear of heights!
-- Phone survey of parents
-- How does fear develop?
-- Falls and near falls
-- Social referencing
7
• Certainty:
40 inch drop
• Uncertainty:
ignore parent posing joy
12 inch drop
don’t cross
use soc. ref.
Parent poses fear, don’t cross
“
“
4 inch drop
joy, cross
ignore parent posing fear
cross
•
D. Conclusions
Autonomous thinkers!
III. Object Perception
-- Young infants have some depth
perception at birth
How many objects in a scene?
-- How well they see depth depends on
cues available
-- Must also learn implications of depth
(e.g., cliffs)
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A. Adults: many sources of info
Partly occluded display:
one source: Featural information:
e.g., shape
pattern
color
texture
etc.
If surfaces have the same features, then
same object
Partly occluded display:
If surfaces have different features, then
different objects
B. Infants?
Needham et al.
4.5 mos
Violation
- of- expectation Method:
-- Show two test events:
expected: consistent with expectation
unexpected: violates expectation
-- If look reliably longer at unexpected, have
expectation
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Similar Condition
Move-Together Event
Results:
-- look reliably longer at apart than at
together event
-- see red surfaces as 1 box
Move-Apart Event
• Assume similar features mean one object
Dissimilar Condition
Results:
Move-Together Event
-- look reliably longer at together than at
apart event
-- see red and green surfaces as 2 boxes
Move-Apart Event
• Assume different features mean different objects
C. Conclusions
-- By4.5 mos, use featural info to organize
scenes
-- Recent work: not at 3 months
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