The Location of Intelligence in the Brain...Found?

August 3, 2000 Newspapers and the Internet were screaming the headlines: "Intelligence Resides in Certain Parts of the Brain" - in Yahoo!News, July 20, 2000 "Scientists Pinpoint Intelligence Zone in the Brain" - in PsycPort, July 21, 2000 "Scientists Say They Have Found Source of Intelligence in Brain" - in the Seattle Times, July 21, 2000 What was this news about and what can be made of this new research? In 1904, Charles Spearman proposed that there was something common to all intellectual abilities and that this general intelligence or "g" factor could be measured. An opposing view was developed by Godfrey H. Thomson in 1916. Thomson believed that intellectual skills required many different abilities. The July 21, 2000 issue of the journal Science published a paper by English and German scientists that sent shockwaves through the media and scientific community. Led by Dr. John Duncan, the research team used positron emission tomography (PET) to measure the brain activity of adults during spatial, verbal and motor tasks. These tasks were designed to measure "general intelligence" or a "g factor." Duncan and his co-workers discovered that the different tasks resulted in increased activity in the same brain area: the lateral frontal cortex (see the figure on the left). They interpreted these results to mean: "...that 'general intelligence' derives from a specific frontal system important in the control of diverse forms of behavior." Does this mean that the lateral frontal cortex is the "intelligence zone of the brain?" Probably not. Robert Sternberg, a professor in the Department of Psychology at Yale University, wrote an editorial that also appeared in Science. Sternberg outlined several flaws in the interpretation of the data: The g factor may not be a good measure of intelligence. Some tests, such as the Scholastic Aptitude Test (SAT) measure specific skills, but may not reflect everyday intelligence. Sternberg reports that US presidential candidates Al Gore and George Bush did not score particularly well on the verbal section of the SAT: Gore received a 625 and Bush received a 566. Despite these low scores, most people would probably agree that Gore and Bush are "intelligent." General intelligence tests do not measure talents such as creativity or adaptability. The design of the experiment permitted the researchers to make correlations only. They found that frontal lobe activity had a relationship to intelligence test data. This type of experiment does not permit conclusions about what caused the relationship. Moreover, Sternberg correctly points out that in some experiments, "more intelligent people" sometimes show less activity in the frontal lobe during analytical tests than "less intelligent people." This may indicate that "smart" people do not have to work as hard on the tests compared with other people. Careful reading of this new research reveals that the media ignored an important point made by Duncan and colleagues. The scientists never said that the lateral frontal cortex is the only area involved in their results. Rather, they believe that: "... g reflects the function of a specific neural system, including as one major part a specific region of the lateral frontal cortex." The exact functions of the lateral frontal cortex are still unknown. Further experiments, perhaps ones that test the abilities of people with damage to the lateral frontal cortex, may shed light on the brain pathways involved with intelligence.

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