The Effects of Age on IQ Tests

The idea that IQ reduces with age is a popular theory and is associated with what is known as the Flynn Effect. In the 1980's, American scientist James R. Flynn carried out studies on IQ scores recorded in the U.S. and other countries around the world over a period of 60 years. His results showed that each generation in each country was scoring more highly than the one before it. Comparisons between older and younger people also showed a higher IQ overall among the young.

However, Flynn and other researchers have cautioned against comparing results across different generations, pointing out how IQ tests have been formulated differently over the years, meaning that researchers are not necessarily comparing like with like.

It's a widely-held belief that human beings are at their most intelligent between the ages of 18 and 26, fitting in neatly with the years during which most college students undertake their studies. However, tests carried out in Case's Mandel School of Applied Social Sciences in Cleveland in 2006 showed that physical fitness, dexterity and young eyes also help students score highly in IQ tests as compared to older people.

In addition to the difficulties some seniors may experience in carrying out IQ tests due to physical slowing down, less acute eyesight and so on, changes in society, attitude and the approach people take to tests may impact IQ scores. This theory is known as the Brand Hypothesis. Although it has subsequently been challenged, it advances the theory that younger people "score better on timed tests because they make intelligent guesses and don't waste time trying to get every test item correct."

Some researchers also believe that better education, with more time being spent in formal education, and better nutrition have improved IQs around the world.

Research carried out in 1992 comparing the IQ scores of seniors with their own scores at 50 years younger showed that any reduction in intelligence associated with age was "minimal."

Other research carried out on the records of 4,300 American ex-servicemen by psychologists at the University of Aarhus in Denmark in 2008 showed that verbal skills kept improving for at least 20 years after the servicemen were first tested at the age of 20. Their arithmetical ability remained at the same level for the same period. This lead the researchers to the conclusion that "elderly brains are slower but sharper."

Between 1997 and 2010, researchers at the University of Aberdeen in Scotland tested 136 people in their 60s, 70s and 80s who, like all Scottish children, had sat IQ tests at the age of 11. The seniors were given brain scans and took mental tests, leading the researchers at Aberdeen to some interesting conclusions. These include that "bright children become bright adults and intelligence is linked with longer life," also that smoking can adversely affect IQ but that fish oils can slow brain aging and that physical activity is good for the brain.