What Is the Evidence for the Heritability of Iq?

What is the evidence for the heritability of IQ?

There has been a continuing debate about the heritability of IQ. IQ can be defined as “a measure of a person's intelligence as indicated by an intelligence test”. Some researchers argue that intelligence is predominantly inherited; others claim it is principally due to one’s environmental factors. The straightforward fact that people in the same family tend to be more alike, and that children born into families with “clever” parents tend to be clever is ineffective alone when discussing this; although we share the same genes as our parents, we also grow up in the environment that they have created for us (Deary, 2001). This very environment that they have created for us (including our nutrition, schooling, health care and so on) is part of many aspects of life as we grow up and may have a significant impact on our intelligence. The principal research in this area focuses on the study of twins (experiments of nature) or adopted children (experiments of society). These 2 groups can help us understand the foundations of our intelligence (Deary, 2001).

Studying twins is a highly important component in the study of the heritability of intelligence. The main interest of researchers in this area is twins who are separated at birth. Genetics-wise, identical twins carry 100% the same set of genes whereas non-identical twins carry around 50%. In cases where twins have been brought up together, there are also 2 types of environmental effects (as well as genetic effects) that are thought to affect their intelligence; common environment and unique environment. Common environment includes anything that is shared with their twin predominantly in family life for example, feeding patterns or parent’s attitudes. The unique environment includes anything that is not shared, for example each twin may have a different set of friends or a different set of hobbies (Deary, 2001). In cases where twins who are separated at...