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Unit 3.docx


Department
Psychology
Course Code
PSYC 251
Professor
Stanka A Fitneva

Page:
of 8
Unit 3: Studying Infants
Chapter 5: Seeing, Thinking & Doing in Infancy
Perception
- sensation: processing basic info from the external world through sensory receptors in the sense organs (eyes, ears, skin,
etc.) & brain
- perception: the process of organizing and interpreting sensory info
Vision
- roughly 40 to 50% of our mature cerebral cortex is involved in visual processing
- newborns’ vision improves extremely rapidly in their first months
evidence provided by the preferential-looking technique (method for studying visual attention, involves
showing infants 2 patterns or 2 objects at a time to see if they prefer one over other)
Fantz (developed technique) showed that newborns prefer to look at something than at nothing
- another method used to study sensory & perceptual development in infants is habituation (repeatedly presenting an
infant with a given stimulus until the infant’s response to it habituates, that is, declines)
once habituated to the stimulus, a novel stimulus is presented
if infant’s response increases, the baby has the ability discriminate b/w the old & new stimulus
Visual Acuity
- visual acuity: the sharpness of visual discrimination
- infants generally prefer to look at patterns of high visual contrast (ie. black-and-white checkerboard) because they have
poor contrast sensitivity (ability to detect differences in light & dark areas in a visual pattern)
- one reason for this poor contrast sensitivity is the immaturity of infants’ cones: light-sensitive neurons highly
concentrated in the fovea (the central region of the retina) & are involved in seeing fine detail & color
- in infancy, cones have a different size & shape & are spaced farther apart than in adulthood
as a consequence, newborns’ cones catch only 2% of the light striking the fovea (65% in adults)
- visual acuity then develops so rapidly, by 8 mts, infants’ vision approaches that of adults, w/ full adult acuity present by
around 6 yrs
- another restriction on young infants’ visual experience is that, for the first mth, they don’t share adults’ experience of a
richly colorful world
at best, they candistinguish some shades from white
- by 2 or 3 mts of age, infants’ color vision is similar to that of adults
4 & 5-mth-olds prefer (look longest at) the samebasic colors that adults rate as most pleasant (red & blue)
also perceive the boundaries b/w colors in more or less the same way as adults do: they respond equivalently to
two shades that adults label as the same color (ie.“blue”), but discriminate b/w 2 shades that adults refer to w/
different
Visual Scanning
- newborns have trouble tracking stimuli in their environment bc. their eye movements are jerky & often don’t stay w/
whatever they are trying to visually follow
- not until 2 or 3 mts are infants able to track moving objects smoothly (only if object moving slowly)
- another limitation on young infants’ visual experience of the world is their restricted visual scanning
w/ a simple figure like a triangle, infants younger than 2 mts look almost exclusively at one corner
w/ more complex shapes, tend to scan only the outer edges
by 2 mts, infants scan much more broadly, enabling them to pay attention to both overall shape & inner details
Pattern Perception
- accurate visual perception of the world requires more than acuity & systematic scanning; also requires analyzing &
integrating separate elements of a visual display into a coherent pattern
- perception of subjective contour results from active integration of the separate elements in the stimulus into a single
pattern (figure below); 7-mth olds also detect the illusory square
Object Perception
- our perception of objects in the world is very stable
- when person approaches or moves away from us, or slowly turns in a circle, our retinal image of the person changes in
size & shape, but we don’t have the perceive them as getting larger or smaller or changing shape
we perceive a constant shape and size (perceptual constancy)
- perceptual constancy: perception of objects as being of constant size, shape, color, etc. in spite of physical differences
in the retinal image of the object
- the origin of perceptual constancy is debated b/w empiricists & nativists:
empiricists argue that our perception of the constant size & shape of objects develops as a function of experience
nativists argue that this perceptual regularity stems from inherent properties of the nervous system
onativist view is supported by evidence of perceptual constancy in newborns and very young infants
oin an experiment, infants looked longer at new cube, indicating they saw it as different in size from the
original one; revealed that they had perceived the multiple presentations of the original cube as a single
object of a constant size, even though its retinal size varied
thus, visual experience is not necessary for size constancy
- another crucial perceptual ability, object segregation: the identification of separate objects in a visual array
- a gap b/w 2 objects provides clear evidence of 2 separate entities, & young infants are sensitive to this information
- importance of movement for object segregation
infants assumed the 2 rod segments they could see were a single, unitary object due to: common movement
the 2 segments always moved together in same direction & at same speed
4-mth-olds who saw Figure 5.4a (2 rods behind block) except the rod was stationary, looked equally long at the
two test displays; in the absence of common movement, the display was ambiguous
for infants, it is common movement that conveys oneness
- with age, infants use additional sources of info for object segregation, including their general knowledge about the world
in the knowledge & object segregation figure, 8-mth olds interpret the two displays differently
perceive the first display as 2 separate objects, but perceive the other display as a single object due to knowledge
about gravity & support
Depth Perception
- to navigate through our environment, we use many sorts of depth & distance cues using objects & landmarks around us
- one depth cue infants are sensitive to very early on is optical expansion, in which the visual image of an object
increases in size as the object comes toward us, occluding more & more of the background
when an image of an approaching object expands symmetrically, we know that the object is headed right for us
- binocular disparity: difference b/w the retinal image of an object in each eye that results in 2 slightly different signals
being sent to the brain
the closer theobject, the greater the disparity b/w the 2 images; the fartheraway, the less the disparity
- stereopsis: process by which the visual cortex combines the differing neural signals caused by binocular disparity,
resulting in the perception of depth
this depth cue is from the fact that we have 2 eyes
arises around 4 mts & is generally complete within a few wks
- monocular or pictorial cues: perceptual cues of depth (such as relative size and interposition) that can be perceived by
oneeye alone
around 6 or 7 mts, infants become sensitive to a variety of monocular cues
also known as pictorial cues, bc. they can be used to portray depth in pictures
Auditory Perception
- the faintest sound a newborn responds to is roughly 4x louder than the quietest sound an adult can detect
not until 5 to 8 yrs does hearing approach adult levels
- auditory localization: perception of the location in space of a sound source
ie. when they hear a sound, newborns tend to turn toward it
Music Perception
- consonant tones are inherently pleasing to human ears, whereas dissonance is unpleasant
- studies have shown infants pay more attention to a consonant version of a piece of music, than to a dissonant one
- infants are sensitive to various qualities of sound:
respond to rhythm
sensitive to temporal organization in music
sensitivity to melody
oafter being habituated to a simple melody, 5 mth-olds heard same melody at higher/lower pitch &
remained habituated
oinfants detection of melody relies primarily on right-hemisphere processing (just like in most adults)
Taste & Smell
- newborns show an innate preference for sweet flavors
- infants are sensitive to smell from birth; they learn to identify their mother in part by her unique scent
also prefer the smell of the natural food source for human infants—breast milk
Touch
- oral exploration dominates for the first few months
- around 4 months, as infants gain greater control over their hand & arm movements, manual exploration increases &
gradually takes precedence over oral exploration
- increasing manual control facilitates visual exploration in that infants can hold interesting objects in order to examine
them more closely
- through active touching, using both mouth and hands, infants explore and learn about themselves and their environment
Intermodal Perception
- intermodal perception: the combining of information from two or more sensory systems
- research on the phenomenon of intermodal perception has revealed that from very early on, infants integrate information
from different senses, linking their visual with their auditory, olfactory & tactile experiences
- Piaget said info from different sensory modalities is initially separate, & only after some months do infants become
capable of forming associations b/w how things look & how they sound, taste, feel, etc.
- in contrast, Eleanor Gibson argued that, from very early on, infants integrate info from different senses
a very simple example is newborns’ auditory localization: their turning toward a sound they hear indicates that
they expect a sound to be associated with an object
very young infants also link their oral & visual experience; in studies, newborns & 1-month-olds could visually
recognize an object they had experienced only through oral exploration
- infants seem especially sensitive to the relation b/w human faces & voices
- by 5 months, infants associate facial expressions w/ the emotional tones in voices
Motor Development
Reflexes
- reflexes: innate, fixed patterns of action that occur in response to particular stimulation
- some reflexes have adaptgive significance:
grasping reflex – newborns close their fingers around anything that presses against the palm of their hand
rooting reflex – when stroked on the cheek near their mouth, infants turn head in the direction of the touch & open
their mouth
sucking reflex & swallowing reflex – initiated by contact w/ nipple; increase the babys chance of getting
nourishment
- other reflexes have no known adaptive significance:
tonic neck reflex – when an infant’s head turns or is turned to one side, the arm on that side of the body extends,
while the arm & knee on the other side flex