Human beings develop in 4 different aspects of growth: Social, Physical, Intellectual, and Emotional. The areas are all interconnected, so when one is affected, it may influence the others.
Intellectual development refers to the development of a person’s mental and thinking abilities.
Brain Growth and Development
At birth, the brain is one-fourth its adult weight. At six months, the brain has grown to half its adult weight. At age two, the brain is three-fourths adult size and weight. Females have a physically smaller brain, but 11% more neurons than males.
The brain is made up of nerve cells called neurons, the majority of which were present at birth. Neurons located in the various lobes or segments of the brain are task specific. This means certain neurons located in certain areas of the brain are responsible for specific tasks.
Neurons are hooked together with varying numbers and kinds of connections called synapses (a neuron and it’s synapses are shown at right). The number of connections results from inherited growth patterns first, and then environmental stimuli and challenge. New learning exercises the brain, causing the blood supply to increase, and leading to a greater supply of oxygen to the brain.
The number of connections, or synapses, determine a person’s capacity to learn. The more synapses, the greater the capacity for learning.
Limitations to Learning
A window of opportunity is a critical period between birth and about the age of 10, in which the brain connections reach their peak. After that time, the brain starts eliminating inactive neurons. It is imperative that the child’s brain is provided proper nourishment, stimulation, challenge, and nurturing during these early years to encourage neuron activity.
The body’s ability to create new neurons, especially after the age of 10, is severely limited if not impossible. If they are destroyed or eliminated, they are gone forever.
(experimental and controversial embryonic stem cell research offers the most promise for restoring permanently damaged or destroyed neurons)
Brain cells (neurons) and connections (synapses) , can also be destroyed by brain injury, chemical abuse, excessive levels of body chemicals produced during stress, and diseases such as Parkinson’s and Alzheimer’s.
Measuring the "Capacity to Learn"
Alfred Binet was born on July 11, 1857 in Nice, France. He was the only child of a physician father and an artist mother. His parents separated when he was very young and he was raised by his mother. Binet attended college in Paris at the age of 15, and received his license to practice law in 1878 and then decided to follow the family tradition of medicine. Nevertheless, his interest in psychology became more important than finishing his medical studies.
In 1905 he developed a test in which he had children do tasks such as follow commands, copy patterns, name objects, and put things in order or arrange them properly. He gave the test to schoolchildren and created a standard based on his data. From Binet's work, the phrase "intelligence quotient," or "IQ," entered the vocabulary. The IQ is the ratio of "mental age" to chronological age. Binet’s tests (the Binet-Simon IQ test) focused on measuring the brain’s capacity for learning rather than on actual achievement. Cognitive psychologist Lewis Terman (1877-1956), while on staff at Stanford University, later revised Binet’s work, with a resulting IQ test still used today: the Stanford-Binet IQ test.
An IQ score indicates the capacity or learning size of the brain…the brain’s potential to learn. It does not measure what actual learning has taken place.
IQ Scores
An Intelligence Quotient indicates a person's mental abilities relative to others of approximately the same age. Intelligence is defined as the capacity for verbal and numerical reasoning.
| Classification |
IQ Scores |
% of population |
| Very Superior |
130 and over |
2.2 |
| Superior |
120-127 |
6.7 |
| High Average |
111-119 |
16.1 |
| Average |
90-110 |
50 |
| Low Average |
80-89 |
16.1 |
| Borderline |
70-79 |
6.7 |
| Handicapped |
Below 70 |
2.2 |
Standard Deviation
Psychologist David Weschler, 1896-1981 developed two well-known intelligence scales: the Wechsler Adult Intelligence Scales (WAIS) and the Wechsler Intelligence Scale for Children (WISC). These are often used today instead of the Stanford-Binet. Scoring on all tests is similar.
Weschler also did work on the scoring of tests, and the use of standard deviations. A standard deviation is a “degree of probable error”.
If you scored 108 on a test, and the standard deviation for that particular test was 3 points, that means your score could be as much as 3 points lower or as much as 3 points higher.
When calculating standard deviation, take the score + or – the deviation.
Mean and Average
When working with statistics and comparing one individual’s test scores to other individuals or a group, it is helpful to calculate “mean” and “average” scores.
A “mean” score is the middle score in the entire range of possibilities. You would take all the scores in a sample group; line them up in order of low to high, and find the middle.
An “average” score is when you add together all the scores in a sample group, and then divide by the total number of samples.
“Mean” and “average” scores for any one test group may or may not be the same. Can you determine the mean and average scores for a group with the following individual test scores?
Answer: 106 is the mean score; 105.8 is the average score
Mental Handicap
When the Stanford-Binet was developed, individuals scoring below 70 were called “mentally deficient”, and the 4 levels of deficiency were labeled from least to most severe as “borderline deficiency, moron, imbecile, and idiot”. Society’s misuse of those terms eventually led to a change. The term “mental retardation” replaced “deficient”, and the words “mild, moderate, severe and profound” replaced previous labels.
Today, the term “mental retardation” has been replaced with “mental handicap”. Mildly mentally handicapped individuals are considered educable. Moderately handicapped individuals are considered trainable.
Name changes have occurred to reinforce the idea that all human beings have value within American society, as well as general acceptability. Even the upper scores have been changed from “superior” labels to “gifted” and “high ability learners”.
| IQ Range |
Classification |
| 50-69 |
Mild |
| 35-49 |
Moderate |
| 20-34 |
Severe |
| below 20 |
Profound |
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