Final: Old chapter on development Flashcards
What are the 2 most common methods used to measure visual acuity in infants?
- using behavior (preferential looking)
- Electrical signals recorded from the scalp (visual evoked potential)
How is acuity determined?
by noting the smallest letters, a person can accurately identify
Stimuli are presented to the infant, and the experimenter watches the infant’s eyes to determine where the infant is looking. If the infant looks at one stimulus more than the other, the experimenter concludes that he or she can tell the difference between them.
Preferential looking technique
Infants preferences to look at certain types of stimuli
Spontaneous looking preferences
TRUE OR FALSE: infants choose to look at objects with contours over ones that are homogeneous
TRUE
As we decrease the size of the bars, can the infants tell the difference between the grating and gray stimuli easier or harder?
Harder, the decrease in the size of the bars it becomes more difficult for infants to tell.
How do we measure an infant’s acuity?
By determining the narrowest stripe width that results in looking more to one side
Recorded by disk electrodes placed on the back of the infant’s head over the visual cortex; the pooled response of thousands of neurons that are near the electrode
Visual evoked potential (VEP)
If the stripes or checks are large enough to be detected by the visual system, the visual cortex generates an electrical response; what is this electrical response called?
Visual evoked potential (VEP)
What is the initial rapid improvement of acuity followed by?
a leveling-off period
After 1 year of age, what is vision like?
Full adult acuity is reached
Why do infants have low acuity at birth?
Their visual cortex is not fully developed
What is the visual cortex like at birth?
It is only partially developed at birth and becomes more developed at 3 and 6 months, the time when significant improvements in visual acuity are occurring.
How are the fovea cones different between infants and adults?
- newborn’s cones have fat inner segments and very small outer segments, whereas the adult’s inner and outer segments are larger and are about the same diameter.
- Infant’s fat inner segments create the coarse receptor lattice with large spaces between the outer segments. In contrast, the thin adult cones are closely packed, creating a fine lattice that is well suited to detecting fine details.
What does the small size of infants’ outer segments mean?
The newborn’s cones contain less visual pigment and, therefore, do not absorb light as effectively as adult cones.
What does it mean that the cone receptors’ outer segments effectively cover 68% of the adult fovea but only 2% of the newborn fovea?
means that most of the light entering the newborn’s fovea is lost in the spaces between the cones and is, therefore not useful for vision.
a measure of the ability to see fine details
visual acuity
Measured by determining the smallest difference between the dark and light bars of a grating at which an observer can still detect the bars.
Contrast sensitivity
How can we determine how an infant perceives objects of different sizes?
measuring contrast sensitivity with a grating of different bar sizes
a number of cycles of the grating per degree of visual angle
Spatial frequency of a grating
Finer bars are generally associated with ____________?
higher spatial frequencies
What does spatial frequency also depend on?
the grating’s distance from the observer
measure of how fine the bar pattern is on the retina.
spatial frequency
Used to determine the contrast sensitivity of gratings with different spatial frequencies, results in a plot of contrast sensitivity versus spatial frequency
Contrast sensitivity function (CSF)
What does the contrast sensitivity function (CSF) indicate?
that adults are most sensitive to gratings with spatial frequencies drops off rapidly above 10 cycles per degree
What do the curves for the 1 to 3 month-old infants indicate?
- the infants’ ability to perceive contrast is restricted to low frequencies
- even at these lower frequencies, the infants’ contrast sensitivity is lower than the adults by a factor of 20 to 100
- infants can see little or nothing at frequencies above about 2 to 3 cycles/degree
at 1 month after birth, what does their vision consist of?
infants can see no fine details and can see only relatively large objects with high contrast.
at 3 month after birth, what does their vision consist of?
the infant’s contrast perception has improved so that the image looks clearly catlike
What is our perception of color determined by?
the action of 3 different types of cone receptors
When does color vision become present?
within the first 3 to 4 months of life
one stimulus is presented to the infant repeatedly, and the infant repeatedly, and the infant’s looking time is measured on each presentation. As the infant becomes more familiar with the stimulus, he/she habituates to it.
Habituation
An increase in looking time when the stimulus is changed
Dishabituation
What does the occurrence of dishabituation mean?
that the second stimulus appears different to the infant from the habituation stimulus
What did Bornstein conclude?
4-month-old infants categorize colors the same way adult trichromats do
Which develops first: binocular disparity or pictorial depth cues?
binocular disparity
What is one requirement for the operation of binocular disparity?
The eyes must be able to binocularly fixate so that the two foveas are directed to exactly the same place.
Do infants have a precise ability to fixate binocularly?
Newborns only have a rudimentary, imprecise ability to fixate binocularly, especially on objects that are changing in depth
The perception of depth due to binocular disparity
stereopsis
What would happen if we presented a random-dot stereogram to an infant?
Since their visual system cannot yet use disparity info, all he/she sees is a random collection of dots
When does the ability to use disparity info to perceive depth emerge?
sometime between 3 1/2 and 6 months of age.
they depend on experience with the environment and the development of cognitive capabilities.
pictorial cues
When do infants begin to use pictorial cues, like overlap, familiar size, relative size, shading, linear perspective, and texture gradients?
between about 5 and 7 months of age
TRUE OR FALSE: young infants can recognize their mother’s face shortly after they are born
TRUE
what percentage of time did newborns look at the mother?
63%
an inability to recognize faces
prosopagnosia
What helps babies recognize their mother?
their hairline: the high contrast border between the mother’s dark hairline and light forehead apparently provides important info about the mother’s psychical characteristics that the infant uses to recognize its mother.
The ability to perceive a unitary object despite the fact that parts of it are out of sight or partly occluded
Object unity
How do infants perceive objects as continuing behind an occluding object?
MOVEMENT
