Genetic Testing Intelligence

For as many years as scientists have been studying and measuring intelligence, debate has raged about whether genetics or environment plays a greater role in our intelligence.

Even though heredity has proven to be quantifiable, or measurable, in many areas, the topic of genetic intelligence remains controversial. Just how much (or how little) of your smarts do you owe to your ancestors?

What IQ Means

IQ stands for Intelligence Quotient. Your IQ score comes from one of several standardized tests designed to measure general intelligence. An average score is 100, with the top three percent of those tested scoring over 130.

IQ tests do not measure creativity, imagination or other unquantifiable factors. Critics have also suggested standardized intelligence tests favor certain cultural and socio-economic groups.

Genetics Intelligence and Environmental Factors

While arguments endure, research indicates that what you are born with is more important than how you are raised. It is ironic, though, that our greatest minds do not seem to agree on just how much heredity matters.

Studies on the role of genetics in intelligence suggest the influence of genetics ranges from 0.4 to 0.8, with 100 percent inherited intelligence being 1.0. Many behavioral scientists generally believe that 70 to 75 percent of IQ is inherited, but that figure remains controversial.

Obviously, there is a wide gulf in the findings of intelligence genetics studies. The data is so disparate because so many factors can affect the outcome.

One problem with trying to nail down a conclusive study is that inherited intelligence is not static. No matter what gray matter you are born with, environment and learning are still heavily involved.

For instance, although vocabulary size is considered heritable and a generally agreed upon sign of general intelligence, no one has ever emerged from the womb spouting SAT words. The argument for genetic intelligence in this case is that words are available to everyone, in all environments, so what you actually learn is up to genetics intelligence.

Intelligence Influenced by Genetics

So is it more important to come from smart parents or to be raised in an environment that is conducive to learning?

Generally speaking, talent trumps effort. Based on the research, a suitable conclusion is that while environment often shapes the raw inherited talent of the mind, the role of genetics in intelligence is powerful.

Studies in intelligence genetics have been conducted using adopted children living together and identical twins brought up apart. The twins, despite being raised separately, are a lot closer in intelligence than adopted children in the exact same environment. Using this research, some scientists have concluded that genetics play a stronger role in intelligence than environment.

Environment and Genetics Intelligence

The role of environmental factors in general intelligence is usually estimated at no more than 25 percent. Most telling is that, despite wide disagreement in the numbers attributed to genetics intelligence, there is no evidence suggesting that our environment can increase intelligence to a relatively high level.

Interestingly, studies have found that as we age, environment becomes less of a factor in developing intelligence. A 1996 paper appearing in American Psychologist found that the influence of genetics on intelligence rises significantly through childhood and adolescence. In part, this accounts for the wide gap in numbers discussed above.

Environmental factors aren’t always positive. A poor environment can be a detriment to IQ, just as one that emphasizes learning can shape and refine a fine mind, like a potter at a wheel of clay. When considering environment, it is important to keep in mind that it is far easier to degrade brain tissue than enhance it.


Davidson Institute (1995). Genetics and intelligence. Retrieved November 11, 2008, from the Davidson Institute Web site: