Physical Development in Infancy and Toddlerhood

Chapter 4 From pg. 133

Learning Capacities

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Learning – refers to changes in behavior as the result of

experience  Babies are born with built-in learning capacities Types of infant learning  Classical conditioning    Operant conditioning Habituation Imitation

Classical Conditioning

 Newborn reflexes allow classical conditioning in young infants  Neutral stimulus is paired with a stimulus that leads to a reflexive response  Once the baby’s nervous system makes the connection between the two stimuli, the neutral stimulus alone with produce the behavior

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Steps of Classical Conditioning

An unconditioned stimulus (UCS) produces a reflexive, or

unconditioned response (UCR)

A neutral stimulus, which does not lead to the UCR, is presented just before, or at the same time as, the UCS If learning has occurred, the neutral stimulus, now called the conditioned stimulus (CS), will produced the reflex, now called a

conditioned response (CR)

Operant Conditioning

  Form of learning in which infants act on the environment and stimuli that follow their behavior change the probability that the behavior will occur again   Reinforcer – increases probability that the behavior will occur again  Ex. Sweet liquid reinforces the sucking response in newborns Punishment – decreases probability that the behavior will occur again  Ex. Sour-tasting liquid punishes newborns’ sucking response, causing them to purse their lips and stop sucking entirely Vital to the formation of social relationships    Baby gazes into adult’s eyes, adult smiles back, infant looks and smiles again Behavior of each partner reinforces the other so that both continue the pleasurable interaction Contributes to development of infant-caregiver attachment

Habituation

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Habituation – gradual reduction in the strength of a

response due to repetitive stimulation  Babies respond more strongly to novelty   After baby has seen a stimulus over and over it is no longer novel and baby will decrease responding (lose interest) Looking, heart rate, and respiration may all decline, indicating a loss of interest

Recovery – new stimulus, or a change in the environment,

causes responsiveness to return to a high level

  Assess infants’ recent

memory

   Habituate infants to a baby face Soon after show baby-face and bald man Novelty preference – infants remember baby-face and look longer at bald man Assess infants’ delayed

memory

   Habituate infants to a baby face After weeks or months show baby-face and bald man Familiarity preference – infants who continue to remember baby-face look at baby-face longer

Imitation

   Infants learn through copying the behavior of others  Certain gestures, head movements, facial expressions  Across all cultures as well as newborn chimpanzees Some researchers believe newborns imitate in the same was as older children and adults  By trying to match the body movements they see with the ones they feel themselves make Mirror neurons underlie these capacities  Specialized cells in the motor areas of the cortex     Fire identically when a primate hears or sees an action and when it does the action itself Allow us to observe another person’s behavior while simulating the behavior mentally Biological basis for of imitation, empathetic sharing of emotions, and understanding other’s intentions Brain-imaging research suggests mirror neurons function as early as 6 months of age

Motor Development

 New motor skills allow babies to explore their bodies and environment in new ways  Sitting upright gives a new perspective on the world   Reaching permits ability to act on objects When infants can move on their own, their opportunities for exploration multiply

Sequence of Motor Development

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Gross-motor development – actions that help an infant

move around the environment  Crawling, standing, walking

Fine-motor development – smaller movements

 Reaching and grasping Sequence of motor development is fairly uniform across children, but there are large individual differences in rates of progress  Cephalocaudal trend – motor control: control head 1 st , control arms and trunk 2 nd , control legs 3 rd  Prodimodistal trend – head, trunk, and arm control appears before coordination of the hands and fingers

Motor Skills as Dynamic Systems

 Dynamic systems theory of motor development   Mastery of motor skills involves acquiring increasingly complex

systems of action

When separate motor skills work as a coordinated system, more effective ways of exploring and controlling the environment are produced  Example: control of the head and upper chest combine into sitting with support

Motor Skills as Dynamic Systems

    Each new skill is a joint product of:  Central nervous system development    The body’s movement capacities The child’s goals Environmental supports for the skill Physical environment strongly influences motor skills because it provides opportunities for exploration  Ex. Infants in homes with stairs learn to crawl up stains at an earlier age Motor development cannot be genetically determined because it is motivated by exploration and the desire to master new tasks Behaviors are softly assembled, allowing for different paths to the same motor skill

Dynamic Motor Systems in Action

  Researchers have discovered that the way babies acquire motor capacities depends on:    The anatomy of the body part in use The surrounding environment The baby’s efforts Means that acquiring motor capacities is not strictly cephalocaudal  Ex. 8 month old babies may reach for a toy with their feet before they will reach with their hands   Because the hip joint constrains the legs to move less freely than the shoulder constrains the arms Makes reaching with arms more difficult, requiring much more practice than reaching with feet

Cultural Variations in Motor Development

  Cross-cultural research shows how early movement opportunities and a stimulating environment contribute to motor development Example: infants in Iranian orphanages were deprived of surroundings that induce infants to acquire motor skills      Spent their days lying on their backs in cribs with no toys Most did not move on their own until after 2 years of age When they did move, constant experience of lying on their backs caused them to scoot in a sitting position rather than crawl Because babies who scoot come up against furniture with their feet, not their hands, they are less likely to pull themselves to a standing position (which prepares them for walking) At 3 to 4 years old, only 15% could walk on their own

Fine-Motor Development: Reaching & Grasping

  Voluntary reaching may play the greatest role in infant cognitive development  Because it opens up a whole new way of exploring the environment  Grasping things, turning them over, and seeing what happens when they are released allows infants to learn a great deal about the sights, sounds, and feel of objects Reaching and grasping start out as gross activities and move toward mastery of fine movements

Milestones of Reaching and Grasping

    Prereaching (newborn-3 months)  poorly coordinated swipes or swings Reaching (3 – 4 months)   Ulnar grasp – clumsy motion in which the fingers close against the palm first with both hands, then with one Transfer object from hand to hand (4 – 5 months) Pincer grasp (9 months)  More coordinated grasp using the thumb and index finger opposably

Hearing Development

    Shift from sensation to perception   Sensation – passive, what baby’s receptors detect when exposed to stimulation Perception – active, organize and interpret what is perceived 4-7 months – sense of musical phrasing  Prefer structured musical sounds 6-8 months – “screen out” sounds from non-native languages  Learn to focus on meaningful sound variations 7-9 months – extend sensitivity to speech structure    Recognize familiar words Natural phrasing in native language Begin to divide the speech stream into wordlike units

Analyzing the Speech Stream

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Statistical learning capacity – ability to analyze speech

for recurring sequences of sounds and extract patterns from complex continuous speech  By analyzing the speech stream for patterns infants acquire a stock of speech structures  Later, infants will learn the meaning of the familiar speech structures they have stored Because communication is multisensory, infants receive support from other senses in analyzing speech  Example: parents teaching infant the word “doll”  Saying “doll” while moving a doll around and sometimes having the doll touch the infant

Vision Development

     Supported by rapid maturation of the eye and visual centers in the cortex 2 months – can focus on objects about as well as adults 4 months – color vision 6 months – visual acuity (fineness of discrimination) 20/20  Scanning the environment and tracking moving objects  Result of increased ability to control eye movements 6-7 months – depth perception  Ability to judge the distance of objects from one another and from ourselves

Depth Perception: The Visual Cliff

    Plexiglas-covered table  Shallow side  Deep side Mother stands on deep side and calls infant Around the time babies crawl they begin to avoid the deep side and react with fear  Meaning they perceive the drop-off Babies figure out how to use depth cues from repeated everyday movements

Milestones in Depth Perception

   3-4 weeks old – motion perception  Blink eyes defensively when an object moves toward their face as if it is going to hit 2-3 months – binocular depth  Occurs because our eyes have slightly different views of the visual field and the brain blends the two images, resulting in perception of depth 6-7 months – pictorial depth & fear of heights  Ex. Receding lines, changes in texture, overlapping objects, shadows cast on surfaces

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Pattern Perception

Contrast sensitivity  Contrast – the difference in the amount of light between adjacent regions in a pattern  If babies are sensitive to (can detect) the contrast in two or more patterns, they prefer the one with more contrast To adults the complex checkerboard has more contrasting elements Because of their poor vision, newborns cannot resolve the small features in the complex pattern

Milestones in Pattern Perception

1 month 2-3 months 4 months 12 months

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Poor contrast sensitivity; prefer single, large simple patterns with high contrast

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Can detect detail in complex patterns Scan internal features of patterns Can detect patterns even if boundaries are not really present Can detect objects even if two-thirds of drawing is missing

4 months 12 months

Face Perception

     Infants’ tendency to search for structure also applies to face perception Birth-1month – prefer simple facelike patterns to other patterns 2 months – can discriminate faces  recognize and prefer mothers’ detailed facial features to those of an unfamiliar woman 3 months – make fine distinctions among the features of different faces Perception of the human face supports infants’ earliest social relationships

Intermodal Perception

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Intermodal stimulation – simultaneous input from

multiple senses

Intermodal perception – perceiving running streams of

light, sound, tactile, odor, and taste information as unified wholes Infants perceive input from different sensory systems in a unified way by detecting amodal sensory properties  Amodal sensory properties – information that overlaps two or more sensory systems  Such as rate, rhythm, duration, intensity, temporal synchrony (vision and hearing), and texture and shape (vision and touch)

Milestones in Intermodal Perception

     Birth-3 months – can detect amodal sensory properties  Ex. After touching an object placed in the palm, infants recognize it visually and can distinguish it from a different shaped object 3-4 months – can relate speech sounds to lip movement 4-6 months – can perceive unique face-voice parings of unfamiliar adults 8 months – can match voices and faces on the basis of gender Intermodal perception facilitates social and language processing and is encouraged and expanded by early parent infant interaction

Understanding Perceptual Development

   How do all these developments occur so rapidly???

Differentiation theory – infants actively search for

invariant features of the environment (those features that remain stable) in a constantly changing perceptual world  1 st – search for invariant, stable features in the environment  2 nd – note stable relationships between features   3 rd Visual patterns, intermodal relationships – gradually detect finer and finer features  Differentiation – analyze or break down invariant features Think of perceptual development as a built-in tendency to search for order and consistency which becomes increasingly fine-tuned with age