Physical development (ii)

At birth, the brain is near adult size

- Growth in individual brain cells- Growth in cerebral cortex

At birth the brain weighs 30% of the adult weight. By age 2yrs, it reaches 70%

4 months: The infant's brain responds to every sound produced in all the languages of the world.

8 to 9 months: Babies can form specific memories from their experiences, such as how to push a ball to make it roll.

10 months: Babies can now distinguish and even produce the sounds of their own language (such as "da-da") and no longer pay attention to the sounds of language that are foreign.

12 months: Babies whose parents say, for example, "Lookeee at the doggiee," will go to the appropriate picture of a dog in a picture book more often than those babies who are talked to in normal, flatter voices.

12 to 18 months: Babies can keep in memory something that has been hidden and find it again, even if it has been completely covered up.  They can also hold memory sequences of simple activities, such as winding up a Jack-in-the-box until the figure pops up.

24 months: Preschool children now have clear pictures in mind of people who are dear to them, and they get upset when separated from these people (even their peers).

30 months:  Preschool children can hold in mind a whole sequence of spatial maps and know where things are in their environment.

36 months:  A preschool child can now hold two different emotions in his mind at the same time, such as being sad that he spilled ice cream on his clothes but glad that he's at a birthday party.

As neurons form connections, they need stimulation to survive. Lack of stimulation could lead to synaptic pruning

Approximately 40% of synapses will be pruned during childhood and adolescence through lack of stimulation

Grows most quickly in comparison to othersIncrease from 70% to 90% of adult weight

between age of 2 to 5 yearsCerebral cortex thickens as mylination

occurs – rapid growth in frontal lobe/cortex

Improvement in physical coordination, perception, attention, memory, language, thinking and imagination linked to mylination

The two areas with marked growth

Neural Development and Plasticity The human brain and nervous system consists of

many highly specialized cells that work together to transmit electrical and chemical signals across synapses

All the neurons a person will ever have – some 100 to 200 billion of them – have already formed by the end of the second trimester, before the brain growth spurt has even begun

The major contributor of the brain growth spurt is the development of a second type of nerve cell, called gliaIt nourishes the neurons and eventually encases them in

insulting sheaths of a waxy substance called myelin The brain shows plasticity up until puberty

Cell Differentiation and Synaptogenesis Neurons assume specialized functions. Influenced

by the sites to which they migrate Cells of the visual and auditory areas

The process of synaptogenesis proceeds rapidly during the brain growth spurt

The average infant has far more neurons and neural connections than adults doNeurons that successfully interconnect with other

neurons crowd out those that don’t, so that half the neurons produced early in life also die early in life

The fact that its cells are highly responsive to the effects of experience

Brain Differentiation and Growth Myelinisation is the process by

which neurons are enclosed in waxy myelin sheaths that facilitate the transmission of neural impulses

The myelin sheath acts like an insulator to speed the transmission of neural impulses, thus allowing the brain to communicate more efficiently with different parts of the body

Myelinisation of the higher brain centers may increase adolescent attention span and explain why they process information faster than elementary school children

Cerebral Lateralisation It is the specialization of brain functions in the left

and the right cerebral hemispheres The highest brain centre, the cerebrum, consists

of two halves connected by a band of fibres called the corpus callosum.Each of the hemispheres is covered by a cerebral

cortexLeft cerebral hemisphere controls the right side of the

body, it contains centres for speech, hearing, verbal memory, decision making, language processing, and expression of positive emotions

Right cerebral hemisphere controls the left side of the body and contains centres for processing visual-spatial information, tactile sensations, expressing negative emotions and non-linguistic sounds such as music

- Reflection of greater capacity of one cerebral hemisphere over the other

- No genetic link to handedness- Language centres may be

opposite- Can be trained – in fact, practice

helps

At 6 months, majority of infants show clear hand preference

90% of 5 year olds have dominant hand

Dominant cerebral hemisphere is the hemisphere responsible for skilled motor action.

Left hemisphere is dominant in right-handed individuals.

In left-handed individuals, motor and language skills are often shared between the hemispheres.

The brains of left-handers tend to be less strongly lateralized than those of right-handers. Many left-handers are ambidextrous.

The two hemispheres of the cortex develop at different rates.

The left hemisphere shows dramatic activity between 3 and 6 years and then levels off.

Activity in the right hemisphere increases slowly throughout early and middle childhood, showing a slight spurt between ages 8 and 10.

There is typically no new growth after adolescence

From the age of 20, brain cells will not reproduce

Gross motor development: big actions that are associated with moving around the environment

Fine motor development: smaller more intentional movements such as grasping and reaching for items within the environment

Basic Trends in Locomotor Development

Motor development proceeds in a cephalocaudal direction

Activities involving the head, neck, and upper extremities precede those involving the legs and lower extremities

The Motor Skills as Dynamic, Goal-Directed Systems views motor skills as active reorganizations of previously mastered capabilities that are undertaken to find more effective ways of exploring the environment or satisfying other objectives

Mastery of motor skills involves integration and blending of various smaller skills

Central Nervous System developmentBody movement capacityGoalEnvironmental support

Acquisition, practice, refinementMotor development is NOT genetically

determined

The Maturation viewpoint describes motor development as the unfolding of a genetically programmed sequence of events which the nerves and muscles mature in a downward and outward direction

The Experiential Hypothesis believe that opportunities to practice motor skills are also very important

Investigators who have charted motor development over the first 2 years of life find that motor skills evolve in a definite sequence

Infants who are quick to proceed through this motor sequence are not necessarily any brighter or otherwise advantaged, compared with those whose rates of motor development are average of slightly below average Therefore, a child’s rate of motor development

tells us very little about future developmental outcomes

These are rough ages

Children who are not given the stimulation or opportunity develop slower

Advise: let the child nap on the floor, do not carry child all the time, avoid using the popular yaoyao sarong

Motor skill Mean age achieved 90% infant attain

Holds head upright, steady 6 weeks 3wks – 4mths

Lift self by arms when prone 2 months 3wks – 4mths

Rolls from side to back 2 months 3wks – 5mths

Grasps cube 3mths 3 weeks 2-7 months

Rolls from back to side 4 ½ months 2-7 months

Sits alone 7 months 5-9 months

Crawls 7 months 5-11 months

Pulls to stand 8 months 5-12 months

Plays pat-a-cake 9mths 3 weeks 7-15 months

Stands alone 11 months 9-16 months

Walks alone 11mths 3 weeks 9-17 months

Builds tower out of 2 cubes 11mths 3 weeks 10-19 months

Scribbles vigorously 14 months 10-21 months

Walks up stairs with help 16 months 12-13 months

Jumps in place 23mths 2 weeks 17-30 months

Walks on tiptoe 25 months 16-30 months

Fine Motor Development Development of Voluntary Reaching

An infant’s ability to reach out and manipulate objects changes dramatically over the first year. Newborns are equipped with a grasping reflex

By 2 months of age, infants’ reaching and grasping skills may seem to deteriorate Reflexive palmer grasp disappears and pre-reaching occurs

much less often

These apparent regressions set the stage for the appearance of voluntary reaching

Achieving motor skills at different stages can help foster perceptual development and self-esteem.

Fine Motor Development Development of Manipulatory Skills

At 4 to 6 months of age the palmnar grasp emerges, which is when an infant grasps objects by pressing the fingers against the palm

The next major step in the growth and hand skills occurs near the end of the first year as infants use their thumbs and forefingers to lift and explore objects The pincer grasp transforms the child into a

skillful manipulator who may soon begin to capture crawling bugs and to turn knobs, dials, etc.

Largely dependent on environmental stimulation and opportunities available

Orphanage children (Iran) – delayed skillsJapanese, rural Indian – discourage early

development because of the dangers involved

Kenya, Jamaica – encourage early sitting, standing

Starts as gross skills that are tuned to fine skills

Development of control – Proximodistal trend i.e. palmer grasp before pincer hold

Depends on visual acuity

Beyond Infancy: Motor Development in Childhood and Adolescence Boys and girls are nearly equal in physical

abilities until pubertyBoys continue to make gains on tests of large-

muscles activities, whereas girls level off or decline

Biological development does not account for all the differences in large muscle performance between boys and girls Nor does it explain the declining performance of

many girls, who continue to grow taller and heavier between ages 12 and 17

Gross motor developmentBodies are more streamlined thus CG shifts

downwards allowing greater balance and more use of the larger muscles

By age 2, gait becomes smooth and rhythmic, leading to running, jumping, hopping, galloping, and skipping.

Individual differences more impressive than gender differences

Lag behind gross motor skills (proximodistal)

Become self-sufficient at dressing and feeding.Great satisfaction from managing their own

bodies.Shoe tying

Mastered around age 6 Requires a longer attention span Memory for an intricate series of hand

movements Dexterity

Scribble – 2nd yearRelated to both cognitive and fine

motor developmentAdvances in perception contribute to

the ability to form letters and words

Except for throwing, no evidence that motor development can be taught.

Preschools, child care centers, and playgrounds need to accommodate a wide range of physical abilities

Criticism of a child’s motor performance, pushing specific motor skills, and promoting a competitive attitude may undermine young children’s motor progress.