Factors Affecting IQ

The most fundamental yet elusive concepts throughout the behavioral sciences involve defining and measuring intelligence. While there is no true consensus on the best way to determine intelligence, a person's intelligence quotient (IQ) is commonly used as a measure of his overall intellectual ability. This IQ score can be affected by a number of factors.

Testing Factors

• Trauma and stress can cause bad guessing and trouble focusing, artificially deflating scores.

  There are many facets to intelligence, and just as many different tests to measure them. The two most prominent intelligence tests are the "Stanford-Binet Intelligence Tes, Fourth Edition" (SB-IV) and the "Wechsler Intelligence Scale for Children, Third Edition" (WISC-III). Both of these tests measure general intelligence -- logical and verbal reasoning skills -- but differ in both the format and the grading scale used. According to the National Association for Gifted Children, while scores between the test are generally correlated, the differing formats and underlying testing mechanisms may result in a higher or lower IQ score based solely on the test style. Other tests measure other facets of IQ, such as emotional or social IQ, which are distinct from general intelligence and may have large discrepancies between the scores. Additionally, IQ scores may be artificially inflated by either correct guessing or artificially deflated by a recent traumatic experience.

Exposure to Toxins

• Alcohol is especially dangerous for developing brains.

  While the brain is still developing, in utero all the way through early adulthood, it is highly susceptible to toxic exposure from smoking, alcohol, and other drugs, all of which have been associated with reduced IQ scores later in life. However, a 2010 study conducted by several Canadian universities has also found a link between manganese and other metals -- such as lead -- in drinking water with decreased IQ scores in children. While these toxins have an effect throughout the life-course, their effects are especially potent in the brain's developing stages.

Parental Factors

• Reading to your children can increase their verbal intelligence.

  While IQ is highly heritable, parents and guardians can help their children to reach their highest IQ potential by providing a stimulating environment. This includes not only "intellectual stimulation," such as books, but also proper nutrition. A 2007 study showed that babies who were breast fed tended to score significantly higher on IQ tests later in life than were formula-fed babies. This is believed to be because the mother's milk contains fatty acids, which provide a greater nutritional value to the developing brain.