Visual Acuity Testing Paired Preference Procedure Forced Choice Preference Procedure Optokinetic Nystagmus Visual Evoked Potential– a form of ERP
Jan 06, 2016
Visual Acuity Testing
Paired Preference Procedure Forced Choice Preference Procedure Optokinetic Nystagmus Visual Evoked Potential– a form of ERP
Sensory Development
Can be used to study visual acuity
Vision Testing
Infant Acuity Testing
Infant Acuity Testing
Davida Teller’s simple test card
ERP: Event Related Potentials
Event Related Potentials
Event Related Potential
Visual Evoked Potential
Infant Vision Testing
Acuity Development
Development of Acuity
At birth
At 12 mo.At 3 mo.
Visual Acuity
At birth, acuity is approximately 20/400 to 20/800
By 4 to 5 months infants are no longer “legally blind” (e.g., 20/200)
Reaches 20/20 between 8 to months VEP suggests faster development– why?
What Infants See
Other Visual Limitations
Can only see high contrast stimuli
Contrast Sensitivity Functions
What infants see
Why is vision so poor?
Is it the eye? Cornea
Astigmatism Iris Lens Retina
Changes in Cones
Cone Development
Scanning
Research on externality effect
Scanning in Newborns
Why is vision so poor?
Color Vision
When can babies discriminate color? Separating Hue, Brightness & Saturation
Categorical Perception of Color R O Y G B I V
Can Infants discriminate color?
Problem in determining color discrimination Color and Brightness are two independent aspects of
any image Confounding color differences with brightness
differences – are infants (or adults) discriminating differences on brightness or color? Brightness is a perceptual characteristic not simply a
physical characteristic– must be determined by testing vision
Solution – in adults. 1) Have adults match different colors for brightness 2) Compare different colors previously matched for
brightness
Matching Brightness – adjust the brightness (not hue) of the inner circle to match that of the outer one
Testing for Red/Green Color Blindness
Can Infants discriminate color? – cont. Problems with adult solution to
brightness/color confound for infant testing Can’t ask infants to ignore color and compare only
brightness Can’t use adult matching data to apply to infants.
Brightness likely differ considerably for babies – because of pigmentation in infants’ eyes.
Brightness matches even from one adult to another and likely same for babies – must test each individual separately
Solution – use a clever habituation task to get babies to IGNORE brightness
Infant Color Discrimination Task
Color Categories
Auditory Thresholds
Tested with High Amplitude Sucking Procedure
Newborns hear above 27 decibels
Can discriminate about 1 note on the musical scale
Sound Localization – cont.
L R
Sound louder and sooner to left ear
Newborn Speech Perception
H.A.S. procedure is also used to study speech perception
P. Eimas: Can newborn discriminate “B” from “P” sounds
Can infants discriminate “R from “L” Or Pittsburgher’s
Harry from Hairy
BPTHAI
Dialect
PGH
Early Speech Perception
Is this a innate specialized ability? Abstraction of ongoing speech Invariance over individuals, gender, dialect Dialect Study (At 11 mo but not 4)
Pittsburgh babies can’t discriminate Chinese from Taiwanese
Can discriminate Pgh from New York Can discriminate 2 novel dialects (Southern from
New York)
Newborn Taste Abilities
Can newborns discriminate the four basic flavors of : Sweet, Sour, Bitter, Salty
Newborns prefer sweet and salty—why?
Sweet flavors can sooth the newborn
Newborn Smell
Newborns react positively and negatively to different smells
Can infants detect the smell of their mothers?
World of the Newborn
What is the world of a newborn like? How does this effect opinion about imitation
research?