Physical Development in Infancy and Toddlerhood
Changes in Body Size and Muscle-Fat Makeup
Babies increase in height 50% in the first year. Birth weight doubles in 5 mo., triples by 1 year.
This growth comes in spurts, preceded by hunger and irritability. Adding baby fat helps baby
maintain temperature. During the second year, babies slim down a bit.
Individual and group differences
Girls are generally shorter and lighter and more fat to muscle than boys, even in infancy
(dramatically differs in adolescence). Ethnic background makes a difference, too, as Asians tend
to be smaller and shorter than Caucasians. African-Americans tend to be larger. The best way to
estimate physical maturity is
a measure of bone development seen through
long bones to see how much cartilage has ossified. Girls’ rate of growth is faster
than boys, as well as resistance to environmental impacts. Girls have lower mortality rates at
every age. Boys have more developmental problems such as stuttering or learning disabilities.
Changes in body proportions
- parts of the body grow at different rates.
– growth moves from top down. Head develops faster than trunk and legs.
- growth moves from center of body outward.
- brain has 100 – 200 billions
, although they aren’t well connected at
birth. Neurons connect over tiny gaps,
, through a chemical communication of
is the process of
some neurons returning to an uncommitted state,
unconnected to others due to lack of stimulation. Some tracks get very well connected due to
repeated stimulation, and to make room for these paths, unused neurons deteriorate.
, which is a fatty coating that allows some neurons to send the neural
message much faster. Not all neurons are myelinated.
Glial cells are the support cells for the
neural system. When a part of the brain myelinates, usually a new ability erupts. (In the early
teen years, the frontal lobes myelinate, allowing for abstract, complex thought.)
surrounds the brain, like the icing on a cake. It makes up 85% of brain weight and
allows humans complex thought and language.
of the 2 sides, hemispheres of the brain allows fro more abilities than if each side had to
do all activities. Each side controls the opposite side of the body. Lefties have less specialization of the
brain, & many are ambidexterous. Brain specialization is evident at birth. Speech sounds trigger more
brain wave activity on the left side, music and other stimuli trigger more activity in the right side of the
brain. Also babies display a preference for a hand early on, possibly due to how the baby lies in the
womb. 10% of people are left handed.