Sensory Development
o
Robert Fantz in
the 1960’s started using the Infant Paired Preference Procedure
Visual Acuity Testing
o
Paired Preference Procedure
o
Forced Choice Preference Procedure
o
Optokinetic Nystagmus
o
Visual Evoked Potential– a form of ERP
Vision Testing
Sensory Development
o
Can be used to
study visual acuity
Infant Acuity Testing
Infant Acuity Testing
Visual Evoked Potential
Visual Evoked Potential
Infant Vision Testing
Acuity Development
Development of Acuity
Visual Acuity
o
At birth, acuity is approximately 20/400 to
20/800
o
By 4 to 5 months infants are no longer “legally
blind” (e.g., 20/200)
o
Reaches 20/20 between 8 to months
n
VEP suggests faster development– why?
What Infants See
Other Visual Limitations
o
Can only see high
contrast stimuli
Contrast Sensitivity Functions
What infants see
Why is vision so poor?
o
Is it the eye?
n
Cornea
o
Astigmatism
n
Iris
n
Lens
n
Retina
Changes in Cones
Cone Development
Scanning
o
Research on externality effect
Scanning in Newborns
Why is vision so poor?
o
The brain?
Color Vision
o
When can babies discriminate color?
n
Separating Hue, Brightness & Saturation
o
Categorical Perception of Color
n
R O Y G B I V
Can Infants
discriminate color?
o
Problem in determining color discrimination
n
Color and Brightness are two independent aspects of any image
n
Confounding color differences with brightness differences – are infants
(or adults) discriminating differences on brightness or color?
o
Brightness is a perceptual characteristic not simply a physical
characteristic– must be determined by testing vision
n
Solution – in adults.
o
1) Have adults match different colors for brightness
o
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.
o
Problems with adult solution to brightness/color confound for infant
testing
n
Can’t ask infants to ignore color and compare only brightness
n
Can’t use adult matching data to apply to infants. Brightness likely differ considerably for
babies – because of pigmentation in infants’ eyes.
n
Brightness matches even from one adult to another and likely same for
babies – must test each individual separately
o
Solution – use a clever habituation task to get babies to IGNORE
brightness
Infant Color Discrimination
Task
Color Categories
Auditory Thresholds
o
Tested with High
Amplitude Sucking Procedure
o
Newborns hear
above 27 decibels
o
Can discriminate
about 1 note on the musical scale
Sound Localization – cont.
Newborn Speech Perception
o
H.A.S. procedure
is also used to study speech perception
o
P. Eimas: Can
newborn discriminate “B” from “P” sounds
o
Can infants
discriminate “R from “L”
n
Or Pittsburgher’s
Harry from Hairy
Early Speech Perception
o
Is this a innate specialized ability?
o
Abstraction of ongoing speech
o
Invariance over individuals, gender, dialect
o
Dialect Study (At 11 mo but not 4)
n
Pittsburgh babies can’t discriminate Chinese
from Taiwanese
n
Can discriminate Pgh from New York
n
Can discriminate 2 novel dialects (Eng. Chinese
from New York)
Newborn Taste Abilities
o
Can newborns
discriminate the four basic flavors of :
n
Sweet, Sour,
Bitter, Salty
o
Newborns prefer
sweet and salty—why?
o
Sweet flavors can
sooth the newborn
Newborn Smell
o
Newborns react positively and negatively to
different smells
o
Can infants detect the smell of their mothers?
World of the Newborn
o
What is the world of a newborn like?
o
How does this effect opinion about imitation
research?
Central Nervous System Development
o
Maturation of the
Cerebral Cortex
o
Neuronal Growth
CNS: How do we study?
o
Positron Emission Tomography (PET)
o
Magnetic Resonance Imaging (MRI)
o
Electroencephalography (EEG)
o
Event Related Potentials (ERP)
n
Event-related potentials are patterned voltage
changes embedded in the ongoing EEG that reflect a process in response to a
particular event: e.g., visual or auditory stimuli
Event Related Potentials
Event Related Potential
CNS Development
o
Sub-Cortical Structures fully developed,
however, there are changes in the Reticular Activating Formation
o
Limbic System: also appear fully developed at
birth, however, changes occur in pathways to higher cortical areas
o
Cerebral Cortex undergoes significant maturation
Stages In Neural Development
•
Proliferation – create new cells
•
Cell Migration – move new cells
•
Differentiation
– elaborate the structure
o
Selective Elimination – paring and pruning
Later
Brain Development
Brain Maturation
o
Beginning around
2 months there is a significant increase in dendritic branching
o
To a lesser
extent, axonal growth
o
And a significant
increase in synapses
Infant Sensory Cortex
Brain
Changes with Age –
4 to 21 years
CNS Development
o
There is an overproduction of dendrites and
axons which results in in subsequent elimination or “pruning”
o
A lack of pruning can lead to mental retardation
and developmental disorders (e.g., autism)
o
Why is there an excess?
CNS Development
o
What determines
which neuronal processes get pruned?
n
Morphology and
space limitations
n
Activity
CNS Development
o
William Greenough has suggested a distinction be
made between:
n
Experience-Expectant Processes: Processes common
to all members of specie which in a normal environment undergo common
overproduction and pruning
n
Experience-Dependent Processes: Storage
processes that reflect individual differences and are primarily related to
formation of new synaptic connections
CNS Development
o
Significant
increase in myelination
n
This results in a
significant increase in the velocity with which neurons transmit their impulses
Brain Maturation