# Developmental psychology/Chapter 5/The Body Matures

Growth is:
* Biologically driven
* Socially guided
* Experience-Expected/Dependant

## Growth Patterns

The physical differences between a 6 year old and 24 month old:
* Height and weight increases
* Lower body lengthens, fat --> muslces - children slim as they grow
The BMI is the lowest at ages 5 and 6 vs. other times in life. Here, the center of gravity moves from the chest to the stomach - allowing new tasks to be fulfilled (doing summersaults, cartwheels).
During the early years of childhood, children grow around 3 inches and gain almost 4.5 pounds.
At the age of 6, a child will pose:
* 3 1/2 ft tall
* weighs 40-50 pounds
* lean
* adult-like body proportions
As the brain matures, motor skills improve. Children at the age of 6 can kick and catch a ball.

## Nutrition

Nutrition is key for a child's development. Poor nutrition, due to less family income, leads to weak immunity and diseases later on. This is likely due to less family income --> more fast food, less excersise and sweetened drinks are common. Historically, low-SES children often are around their grandparents - who may encourage the children to overeat due to their past experiences (famines or frequent food shortages, for example). This may lead to chidren eating for the sake of it vs. being hungry, which may lead to overreating - and potentially, diabetes or strokes.
All childrens' appetite, ages 2-6, decrease - so it is essential that the parents feed their children with the right foods and NOT encourage them to overreat. Parents need to realize that underestimating their child's weight is detrimental when it comes to eating habits. Children ages 2-6 are NATURALLY low in BMI. Western diets are normally unhealthy vs. diets in undeveloped nations.

### 2012 statistics of Obesity in the USA

* 8% of 2-5 yrs old
* 18% of 6-11 yrs old
* 21% of 12-19 yrs old
* Obesity rates fell from 12.1% [2010] to 8.4% [2012], though rates rose to 13.9% [2016].

### Other Issues Tied with Obesity
#### Tooth Decay

* Tooth Decay: Too much sugar, sugary drinks and very little fiber
* Baby teeth are replaced by adult teeth by ages 6-10. Poor oral health leads to jaw/speech issues and other infections.
* Tooth infections in pregnant adults potentially can cause preterm births.

#### Food Allergies

3-8% of children are allergic to a specific food. Many of these allergies are outgrown. Young children who eat unhealthy foods trickled in saturated/trans fatty acids usually develop asthma.

## Brain Development

At 2 yrs, most neurons have connected with their fellow neurons and pruning has already taken place. From 75% (2yrs) of its adult weight to 90% (6yrs), myelin is a crucial part in the weight gain (despite pruning out the dendrites).
* Myelin: Fatty substance that covers the neurons in the brain which increases the transmission of messages (neural impulses) from neuron to neuron. It is very useful in the brain as it aids coordination between the two hemispheres through the corpus callosum, a thick band of fibers that connects both hemispheres and allows communication between the two.
* Brain balancing is key, which is why dances are done by 6 years old rather than 2-year-olds. In normal cases, the left half of the brain controls the right side of the body and areas pertaining to logic and skills. The brain's right half controls the left side of the body and areas dealing with emotion and creativity.

### The Development of the Pre-frontal Cortex

The pre-frontal cortex has no connections to the rest of the brain at age 1, very few at age 2 and then gradually improves until age 25. By age 6, we're able to see progress in this:
* Increased gradual sleep
* Emotions are more responsive
* Less temper tantrums
* Less random laughter and tearing up
An example of this is "Simon Says". Children fail at this game because they cannot differentiate between what they've been told vs. what they've seen.
Neurons have an on/off "switch". This is done by a number of biochemical messages from the dendrites to axons and to the neurons. This prevents an adult from being too impulsive or cautious. But children exhbiting poor impulse control is normal. A child may lack the neurological development to focus on a task at hand, jumping from one toy to another (for example). On the other hand, a child may exhibit preservation (the tendency for a child to be "preserved" in a certain matter).
Rest assure, parents! No child is going to master this, as the immaturity of the pre-frontal cortex renders it almost useless in trying to control the limbic system (brain dealing with emotional responses). Since children's neurological abilities increase, they will be better as time progresses. Studies on children ages 3-6 found that children increase in obedience to what adults ask of them. Soon, they're able to switch gears regarding whatever topic they're on (Chinese history vs. Mathematics) thanks to brain maturation (innate) and emotional controlling (learned).

### Impact of Stress

A bit of stress is beneficial as it can improve cognition, but too much of it is, like everything else, detrimental. Excessive stress can damage brain pathways.