IQ and Age
Brainpower declines after age 30
IQs are adjusted for age to offset the cognitive decline that attends aging. IQ peaks between 25 and 29 years old, then drifts down through the working years, with decline becoming more steep after age 70. The graph below from http://hiqnews.megafoundation.org/Definition_of_IQ.html shows how Wechsler IQs vary with age:
Adult IQ rankings same as in childhood (Brainpower declines, but IQ stays the same in any age group.)
The Daily Telegraph of London reported that: People who sat an IQ test at the age of 11 in 1932 were ranked in exactly the same order when they took the exam again at the age of 77, showing that intelligence is stable throughout life. Researchers tested 300 pensioners from Aberdeen who took part in the first Scottish Mental Survey of 1932. These included tests of arithmetic, logic and verbal reasoning. Researchers also found that those with high IQs tended to live longer because they made the right health decisions during their lives.
From the article: "Longevity is linked to IQ," By Auslan Cramb, September 28, 2000 http://www.telegraph.co.uk/connected/main.jhtml?xml=/connected/2000/09/28/ecnage28.xml
IQ and the aging process
There is intense debate among psychologists on whether intelligence declines with aging. This chart represents the majority opinion that, after early adulthood, IQ is level but its components change. IQ is a combination of these two curves:
Fluid intelligence(also called "native mental ability") is the information processing system. It refers to the ability to think and reason. It includes the speed with which information can be analyzed, and also includes attention and memory capacity.
Crystallized intelligenceis accumulated information and vocabulary acquired from school and everyday life. It also encompasses the application of skills and knowledge to solving problems.
Many studies have shown that fluid intelligence is more likely to decline with age than crystallized intelligence. In fact, crystallized intelligence may continue to improve with age. Many people continue to gain expertise and skills in particular areas throughout life.
Information from: The American Federation for Aging Researchhttp://www.healthandage.com/html/min/afar/content/other6_1.htm
IQ tests can measure both types of intelligence in the chart above. For example, the Wechsler Adult Intelligence Scale (WAIS). measures crystallized intelligence in most of its verbal subtests, while fluid intelligence is measured by its performance subtests. Starting in 2004, theSAT test has been changed, placing greater emphasis on crystallized intelligence. It now emphasizes course material studied in high schools rather than innate intelligence.
The unexplained "Flynn effect"(the apparent rising of average IQ scores over time) is mostly related to fluid intelligence. Flynn writes: "Different kinds of IQ tests show different rates of gain: Culture-reduced tests of fluid intelligence show gains of as much as 20 points per generation (30 years); performance tests show 10 -- 20 points; and verbal tests sometimes show 10 points or below. Tests closest to the content of school taught subjects, such as arithmetic reasoning, general information, and vocabulary, show modest or nil gains. More often than not, gains are similar at all IQ levels." One of the best analyses of the Flynn effect is at the bottom third of http://www.vdare.com/sailer/lynn_and_flynn.htm That site's graph of 124 IQ studies from 1914 to 1998 indicates that European vs African IQ's maintain their same relative positions, while Asian IQ's may be increasing.(perhaps due to better child nutrition).
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