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Chapter 5

Chapter 5 - Seeing, Thinking, and Doing in Infancy.docx

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Ori Friedman

[ 5 ] – SEEING, THINKING, AND DOING IN INFANCY  Dvlmt in 4 closely related areas: - perception - action - learning - cognition  Focus primarily on infants and toddlers  Reason for concentrating on this period: st - extremely rapid dvlpmtal change occurs in all 4 areas during 1 two years of child’s life - dvlpmt in 4 domains particularly intertwined in this period: minirevolutions that transform infants’ beh’ and exp’ in one domain lead to minirevolutions in others PERCEPTION  Infants come into the world w/ all their sensory systems f’n’g to some degree and that subsequent dvlpmt occurs at a very rapid pace  Sensation = processing of basic info from external world by sensory receptors in sense organs and brain  Perception = process of organizing and interpreting sensory info about the objects, events, and spatial layout of our surrounding world Vision  Newborns begins visually exploring the world minutes after leaving the womb  Although newborns dN see what they look at as clearly as adults, their vision improves extremely rapidly in their first mths - method 1: achieved w/ preferencial-looking technique—diff visual stimuli are typically displayed on two side-by-side screens; if infant looks longer at 1 of 2 stimuli, researcher can infer that baby is able to discriminate btwn them and has preference for one over other  newborns would rather look at something than nothing - method 2: habituation—repeatedly presenting infant w/ given stimulus until infant’s response to it declines/habituates; then, novel stimulus presented; if infant’s response i˄, researcher infers that baby can discriminate btwn old and new *both have been enormously powerful for studying infants’ perception and understanding of the world Visual Acuity  New methods enabled researchers to assess infants’ visual acuity—how clearly they can see i.e. showing plain gray square paired w/ black and white stripes of varying widths - b/c infants prefer looking at a pattern to a homogenous surface, narrowest stripes an infant prefers relative to gray square is assumed to be smallest pattern distinguishable  Dvlp’s so rapidly that by 8mths, vision approaches that of an adult, and full adult acuity present by around age 6  Contrast sensitivity = ability to detect diffs in light and dark areas in a visual pattern - young infants have poor cs i.e. generally prefer to look at patterns of high visual contrast—such as black and white checkerboard - a reason: immaturity of cones—light-sensitive neurons involved in seeing fine detail and colour  For the first month or so, dN share adults’ exp’ of a richly colourful world Visual Scanning  From beginning, attracted to moving stimuli (have trouble tracking b/c eye mvmts are jerky and often dN stay w/ object they are trying to follow) - not until 2 or 3 mths are they able to track moving objects smoothly & only IF object is moving slowly  Visual scanning is restricted - w/ simple figure like a triangle, < 2mths look almost exclusively at one corner - w/ more complex shapes, tend to scan only outer edges Pattern Perception  Able to perceive coherence among moving elements i.e. film of moving points of light: moving lights appear to be attached to mj jts and head of human being - adults: immediately and confidently identify person walking - 5mths: apparently see same thing; look longer at points-of-light displays that suggest human mvmt than ones that dN Object Perception  Perceptual constancy = perception of objects as being constant size, shape, colour, etc., despite phys diffs in retinal image of object  Study of size constancy: - newborns repeatedly shown cube at varying distances, so size of retinal image projected by cube differed from one trail to next - q’n was whether newborns would perceive these events as multiple presentations of a single obehjct or as ~ objects of diff sizes  to answer q’n: - present newborns w/ original cub along w/ 2 ndone (identical except twice as large) nd - crucial factor: 2cube twice as far away as original one, so it produced same-size retinal image as original  infants looked longer at new cube, indicating that they saw it as diff in size from original one  revealed that they had perceived the multiple presentations of original cube as a single object of a constant size, even though its retinal size varied  Object segregation = perception of separate objects in a visual array  Experiment: importance of motion for object segregation - 4-mth-olds presented w/ display which adults perceive as a single rod moving back and forth behind a block of wood - after habituating to display, infants shown two test displays - if infants (like adults) assumed that there was a single rod behind the block during habituation, they would look longer at the two rod segments b/c that display would be novel - this is exactly what the babies did - what caused infants to assume that the two rod segments they could see were a single, unitary object?  common mvmt - even 2-mth-olds perceive single rod if block is quite narrow so that more of the rod is visible as it moves back and forth  Common mvmt is such a powerful cue that it makes even perceptually distinct elements look like a unitary object - dN matter if two parts of object moving behind block differ in colour, texture, shape, or how they move Depth Perception  From beginning, infants are sensitive to some of these cues, and they rapidly become sensitive to the rest  Optical expansion = object comes toward us, its visual image i˄’s in size, causing more and more of bg to be occluded - when an image of an approaching object expands symmetrically, we know the object is headed right for us, and a sensible response is to duck - babies cannot duck, but infants as young as 1 mth old blink defensively at an expanding image that appears to be an object heading toward them  Binocular disparity = differences btwn retinal image of an object in each eye the results in 2 slightly diff signals being sent to the brain - the closer the object we are looking at, the greater the disparity btwn the two images - the farther away the object, the less the disparity  Stereopsis = visual cortex computes degree of disparity btwn eyes’ differing neural signals, resulting in perception of depth  6-7mths: begin to become sensitive to a variety of monocular depth cues (aka pictorial cues) i.e. relative size: objects that are larger appear to be nearer than smaller objects i.e. interposition: closer objects partially occlude ones that are farther away Auditory Perception  Faintest sound a newborn responds to is roughly 4x louder than quietest sound adult can detect - not until age 5-8 does hearing approach adult levels  Auditory localization = perception of location in space of a sound source  b/c they turn their heads very slowly, newborns are most likely to localize source of sound that cont’s for several seconds Music Perception  recent research shows that infants’ response to music is ~ to that of adults - infants share strong preferences that adults have for some musical sounds over others i.e. argued that consonant tones are inherently pleasing to human ears, whereas dissonant is unpleasant  studies have shown that infants pay more attention to consonant version of a piece of music, whether folk song or minuet, than to a dissonant one  respond to rhythm in music - dN exactly tap toes in time to beat, but do move to it (bounce perceptibly while listening to lively, rhythmic band music)  likewise sensitive to temporal organization in music i.e. study: infants as young as 4½ mths listened longer to Mozart minuets w/ 1-sec pauses btwn natural musical phrases than to same music w/ pauses inserted in middle of phrase  sensitivity to melody - respond like adults, who perceive a melody to be the same regardless whether it is played on a piccolo/tuba, but perceive it to be a diff tune of notes are rearranged Taste and Smell  innate preference for sweet flavours  prefer smell of breast milk—natural food source for human infants  smell plays a powerful role in how a variety of infant mammals learn to recognize their mothers  probably same for humans Touch  important way that infants learn about env’ is through active touch  oral exploration dominates first few mths - through it, presumably learn about own bodies (or at least parts they can get mouth on), as well as texture, taste, and other properties of objects they encounter  4mths: manual exploration i˄’s and gradually takes precedence over oral - actively rub, finger, probe, and bang objects, and actions become i˄’gly specific to properties of objects i.e. rub textured objects; bang rigid ones - i˄ in manual ctrl also facilitates visual exploration in that infants can hold interesting objects in order to examine them more closely, rotating objects to view them from diff angles and transferring them from hand to hand to get better view Intermodal Perception  Intermodal perception = combining of info from 2/more sensory systems as a unitary, coherent event  very early on, integrate info from diff sense i.e. newborn turns toward sound they hear, indicating babies expect sound to be associated w/ object  link oral and visual exp’  link visual and tactile exp’  auditory-visual intermodal perception MOTOR DEVELOPMENT Reflexes  start off w/ some tightly organized beh’s  reflexes = innate, fixed patterns of action that occur in response to particular stimulation  some have clear adaptive value; others have no known adaptive significance  grasping—newborns close fingers around anything that contacts palm of hand  touch cheek near mouth sets off rooting—babies turn head in direction of touch & open their mouth  thus, when cheeks comes into contact w/ mother’s breast, turn toward and open mouth  oral contact w/ nipple then sets off sucking, followed by swallowing - both i˄ baby’s chance of getting nourishment and ultimately surviving  tonic neck—when infant’s head turns or is turned to one side, arm on that side of body extends, while arm and knee on other side flex  reflexes not fully AT i.e. rooting more likely to occur when infant is hungry i.e. tonic neck seems to involve effort by baby to get and keep its hand in view  presence of strong reflexes at birth is a sign that newborn’s central NS is in good shape  most neonatal reflexes disappear on regular schedule, although some (i.e. coughing, sneezing, blinking, and w/drawing from pain) remain t/o life - persistence of reflex beyond point at which it is expected to disappear can indicate neurological problem Motor Milestones  achievement of each (especially walking) constitutes major advance in infant’s exp’ of the world  varies from one society to another i.e. some cultures actively discourage early locomotion - modern urban China: infants typically placed on beds and surrounded by thick pillow to keep them from crawling on dirty floor  infants who undergo exercise regimes are advanced in their motor-skill dvlpmt Current Views of Motor Development  early motor dvlpmt results from confluence of numerous factors that include dvlp’g neural mechanisms-- i˄’s in infant’s strength, posture ctrl, balance, & perceptual skills, and changes in body proportions and motivation  all parents—and many researchers—have impression that infants derive pleasure from pushing envelope of their motor skills The Expanding World of the Infant Reaching  once infants can reach for and grasp objects, they no longer have to wait for the world to come to them - however, reaching takes time to dvlp  1 few mths: limited to prereaching mvmts—clumsy swiping toward general vicinity of objects they see  3-4mths: begin to successfully reach for objects; mvmts still somewhat jerky and poorly ctrl’d  improved ctrl of head and upper torso, made possible by i˄’d muscle strength in neck, shoulders, and arm, are key to making reaching possible  7mths: ability to sit (i)’ly, reaching becomes quite stable, trajectory of reaches consistently smooth and straight to target  stable sitting and reaching  can now lean forward to capture objects previou
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