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?