Where Does Intelligence Come From?

By — John Wiley & Sons, Inc.
Updated on Jan 1, 2011

Children's intelligence can be influenced at birth by heredity (genes), prenatal toxins (such as a mother consuming alcohol or drugs during pregnancy), chromosomal defects (such as Down syndrome), or birth trauma (such as lack of oxygen, which may occur for a number of reasons such as having the umbilical cord wrapped around the neck). A child's environment can also have a powerful influence on intelligence. Some children have many opportunities to learn because they are exposed to a wide variety of learning experiences. Other children may have less exposure to new situations and consequently may experience less opportunity for learning. Unfortunately, intelligence can also be lowered by exposure to brain injury (accident) or environmental toxins, including exposure to lead-based paint or drugs such as inhalants.

Although IQ scores can predict academic and later occupational success, merely having a high IQ does not ensure success. Intelligence tests do not measure motivation or other more subtle learning problems, such as difficulties with memory, that might interfere with success.

Remember: IQ scores are considered more stable with increasing age, and IQ scores obtained for preschool children should be regarded cautiously because they are not as reliable. Some young children may score lower than their true ability due to a lack of experiences or fewer opportunities, whereas others may score higher because they live in an environment rich in experiences.

How is the IQ Score Calculated?

The easiest way to understand IQ scores is to relate mental age (MA) or the mental capacity based on the test score, to chronological age (CA), or the actual birth age. For example, if Donny is five years old (CA) but he has the mental age (MA) similar to that of a four-year-old (MA), we would calculate his intelligence score by dividing the MA by the CA and then multiplying the result by 100. In our example, the resulting intelligence score would be 80. Because the average IQ score is 100, then Donny's intelligence score would be below average.

Although the actual mathematical computation of IQ is more complicated, these examples should provide a general idea of what an IQ score means. It is not uncommon for some individuals to be skeptical and concerned about the use of IQ scores in the educational system and how this information might be misused (for example, if a child's IQ score is below average, does that mean the expectations for success will be lower?). Although expectations can influence behavior, the benefits of knowing a child's IQ far outweigh any potential risks. The positive side of knowing an IQ is that it helps us to understand, at a basic level, where a child's problem-solving abilities are in relation to other children at the same age level. Furthermore, as we will soon discuss, IQ is not a single score; the IQ score is actually a composite score based on a number of tests (subtests) that measure different areas of functioning. When we look at the subtest scores, we often can find patterns of strengths and weaknesses that can assist greatly in developing an individualized education program (IEP). Later, we will discuss how the child's initial IEP is developed based on results and recommendations from the initial comprehensive assessment, which often includes intelligence testing.

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