IQ Test Results: What Factors Can Influence Them?

Background

Most researchers agree that genetic factors account for about 40-80% of the variation in IQ test results. If this is true, then environmental or other factors must account for 20-60% - which is a large range.

Factors Influencing IQ

Some environmental factors that have a large effect upon later IQ test results include prenatal ones, such as:

• Whether or not, prior to the birth, mother drank large amounts of alcohol during her pregnancy (fetal alcohol syndrome).
• The mother was exposed to large amounts of lead.

Factors that have an effect during the early years

Other factors that have their influence on IQ at a young age are:

• Schooling.
• The quality of toys used.
• The amount of external stimulus the child was subjected to.
• Prolonged malnutrition also has a marked negative effect on IQ test.
• In contrast, babies who were breastfed have IQs up to 10 points on average higher than those who weren