Visual Development in Human Infants

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Visual Development in Human Infants
Karen DobkinsPsychology DepartmentUC San Diego
Todays lecture http//psy.ucsd.edu/kdobkins/
HDPnotes.ppt
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OUTLINE
- Brief overview of neural development
- Methodology of Psychophysics
- 3 Stories in Infant Vision (Ages 1 - 6 months)
1) PATTERN VISION Grating Resolution, Snellen
acuity
2) COLOR VISION Red/Green vs. Black/White
Sensitivity
3) MOTION PERCEPTION (if theres time)
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Why Study Development?
1 Clinical Applications
e.g., Children with Dyslexia Autism William
s Syndrome have trouble with Motion, but not
Pattern or Color, Vision
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Why Study Development?
2 What are the Perceptual consequences
of Neural changes during postnatal development?
Exuberant connections, then pruned away
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Another Example (specific to the visual system)
But first. a little background in VISION
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GRATING STIMULUS
Sensitivity
2 properties 1) Contrast
(max-min)/(maxmin) 100
High Contrast
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GRATING STIMULUS
Resolution (or Acuity)
(like Snellen eye charts, but using GRATINGS, not
letters!)
2) Spatial Frequency (cycles/deg)
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How are these stimuli seen by the Eye?
THE EYE
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BACK TO DEVELOPMENT
Infant Photoreceptors in the Eye
A) Immature Morphology
Do not capture light well, have low sensitivity
to light
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Infant Photoreceptors in the Eye
B) Immature Density
Do not resolve stimuli well
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THE EYE
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Infant Photoreceptors in the Eye
B) Immature Density
Do not resolve stimuli well
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So. How can we actually measure contrast
sensitivity and grating resolution in
pre-verbal INFANTS?
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In adults a simple detection task
Is the stimulus on the LEFT or RIGHT? (called a
2-AFC)
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In Infants Forced-Choice Preferential Looking
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Contrast Sensitivity
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STORY 1 PATTERN VISION IN INFANTS
Spatial Contrast Sensitivity Function

• Tells us about Contrast Sensitivity
• at different Spatial Frequencies

2) tells us about Resolution
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STORY 2 COLOR VISION IN INFANTS
Testing this proposal INFANTS DONT SEE
COLORS VERY WELL!
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Development of Sensitivity for Chromatic
(Red/Green) vs. Luminance (White/Black)
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Observers Correct
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Infants possess equally low sensitivity for BOTH
Luminance (Black/White) and Chromatic (Red/Green)
stimuli
INFANT COLOR VISION IS RELATIVELY FINE!!
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STORY 3 MOTION VISION IN INFANTS
Speed Contrast Sensitivity Function
Obtain Contrast Sensitivity at different
Moving Speeds (keep SF constant)
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Speed tuning develops fast!
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Thank you!
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Speed tuning develops fast!