Seeing, Thinking, and Doing in Infancy

Transcription

1 Seeing, Thinking, and Doing in Infancy How Children Develop Chapter 5

2 Infant Development Perception Action Learning Cognition

3 Motor Development Reflexes Motor Milestones Current Views of Motor Development The Expanding World of the Infant

4 Infancy: Motor Development Newborns neonates are surprisingly capable. Which capacities are innate? Which require maturation? Which develop through interaction? Are there discontinuities?

5 Newborn Reflexes A reflex is The Organized Newborn Often used to judge neurological damage early in life SURVIVAL REFLEXES: Serve obvious physical needs breathing sucking eyeblink rooting swallowing pupillary

6 Newborn Reflexes A reflex is The Organized Newborn Often used to judge neurological damage early in life PRIMITIVE REFLEXES: Serve no obvious physical needs; may be vestiges of important reflex behaviors at earlier stages of human evolution moro tonic neck stepping Palmar Babinski swimming

7 Reflex Procedure/response Does what? Rooting Stroke cheek near mouth baby turns head Sucking Finger in infant s mouth infant sucks Moro More specifics on reflexes Palmar grasp

8 Adaptive Value of Reflexes Many have survival value: Sucking crucial to eating. Others protect infants: Eye blink protects from stimulus. Others encourage gratifying interaction: Sucking for feeding, Palmar for physical contact. Some no longer needed: Moro reflex helps baby cling to mother - but in West babies not carried all day.

9 Reflexes and motor skills Disappear by 6 months as voluntary control increases. Issue: Are reflexes building blocks for voluntary control? 1. Babies adapt reflexes: Palmar changes depending on how palm is stimulated. 2. Some reflexes disappear but return later: swimming & stepping.

10 How do reflexes contribute to motor control? Zelazo (1983): Practice stepping increases spontaneous stepping movements. Hence, exercising reflex helps develop area of cortex related to movement. No exercise, reflex disappears. Thelen (1983): Weight gain not matched by leg strength. Exercise builds muscles reflex retained.

11 The Fish Tank Experiment (Thelen, Fisher, & Ridley-Johnson, 1984)

12 The Fish Tank Experiment (Thelen, Fisher, & Ridley-Johnson, 1984) 25 Average Steps per Minute Out-of-Water In-Water

13 Weighting the Legs (Thelen, Fisher, & Ridley-Johnson, 1984) 25 Average Steps per Minute Without Weights Weights Added

14 How do reflexes contribute to motor control? Zelazo (1983): Practice stepping increases spontaneous stepping movements. Hence, exercising reflex helps develop area of cortex related to movement. No exercise, reflex disappears. Thelen (1983): Weight gain not matched by leg strength. Exercise builds muscles reflex retained. So, should parents encourage walking reflex?

15 Motor Development The organization and sequence of motor development 1. Gross motor development: actions that help infant get around crawling, standing, walking. 2. Fine motor development: smaller movements reaching & grasping.

16 Milestones of Motor Development

17 Infancy Differentiation and integration in Postural Control, Locomotion, and Manual Control leads to: Improvements in timing, balance, and coordination Motor advances lead to:

18 Infancy Differentiation and integration in Postural Control, Locomotion, and Manual Control leads to: Improvements in timing, balance, and coordination Motor advances lead to: 1. opportunities for 2. better understanding 3. more accurate judgments 4. more interaction

19 The developmental sequence of motor skills is quite uniform. But, large individual differences in rate of development: Motor skill Average age Range (90% infants) Grasps cube 3 months 3 weeks 2-7 months Crawls Walks alone Often, a baby is slow on some motor skills but advanced on others. We are concerned only if slow on many skills.

20 Developmental norms imply maturation: a hard-wired sequence directed by motor development genes But: Interaction of multiple factors, each of which may be influenced by genes and experience

21 Psychologists ignored motor development for 40 years because of maturationist assumptions: Early pioneers Arnold Gesell and Myrtle McGraw believed that motor skills were determined mainly by neurological maturation of the brain. (Perspective = Nature, Passive Child)

22 Motor Skills as Dynamic Systems (Thelen, Pick, Smith) Dynamic systems theory (DNS) views motor development as acquiring ever more complex systems of action Not just development of independent skills: 1. head and chest control combine into sitting with support 2. crawling, standing, and stepping combine for walking.

23 Dynamic Systems Approach New forms emerge through processes of self-organization patterns and order emerge from the interactions of the multiple components of a complex system without explicit instructions from organism or environment

24 Extraordinarily complex structural patterns can emerge from very simple initial conditions in dynamic systems During development, living things with particular properties spontaneously organize themselves into patterns Movie: Baby body sense

25 Evidence for DS Microgenetic research (Thelen, 1994) Attach mobile to 3-month-olds legs. Infants usually kick with one leg or two in alternation. Attach mobile so that two legged kick works best Infants soon learn, and start to use, two legged kick.

26 Locomotion At around 8 months of age, infants become capable of selflocomotion for the first time as they begin to crawl Infants begin walking independently at around 13 to 14 months of age, using a toddling gait

27 Integration in locomotion

28 Locomotion Karen Adolph and her colleagues have found that infants do not transfer what they learned about crawling down slopes to walking down them

29 Back-Lying and Locomotion The campaign to get parents to put babies to sleep on their backs to reduce the risk of SIDS seems to make infants less likely to roll over on schedule It may be that the better view of the world from their backs results in less motivation to roll over It may also be that spending less time on their tummies causes arm strength to develop more slowly By 18 months of age there were no differences in the development of infant crawling

30 Fine Motor Development: Voluntary Reaching Reaching plays big role in infant cognitive development. Grasping allows exploration of new things. Newborns reach out for objects prereaching poorly coordinated. Voluntary reaching begins at 3 months infants reach in dark and light just as well. Hence, does not require visual guidance instead proprioception allows vision to focus on other things.

31 Nature of grasp varies: After reflex comes ulnar grasp fingers close against palm. By months, use pincer grasp with thumb and index finger. By 12 months or so, reaching & grasping executed smoothly.

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33 The Impact of Culture Mothers in Mali believe it is important to exercise their infants to promote their physical and motor development The maneuvers shown here do not harm the babies and do hasten their early motor skills

34 The Impact of Culture Mothers in Mali believe it is important to exercise their infants to promote their physical and motor development The maneuvers shown here do not harm the babies and do hasten their early motor skills

35 Summary of influences on Motor Development Biological Contributions 1. Twins develop motor control at similar rates 2. Blind and disabled children acquire motor skills though later Experiential Contributions 1. Twins study from video 2. Practice accelerates motor development 3. Cultural effects