Human intelligence is an elusive quality. We all think we know it when we see it but try to pin down that quality to a firm, testable definition and suddenly, even for the most experienced researchers, the concept disappears. But now a team of British and German scientists believe they have firmly nailed down at least part of the notion of intelligence. They claim to have found a location for intelligence, whatever it is, in the brain.
For many years researchers have believed that intelligence is a quality which is spread throughout the whole human brain. Traditional psychologists such as Benjamin Martin believe that this accounts for incidences where physical damage to the brain need not affect intelligence at all. By using advanced scanning equipment, however, researchers led by John Duncan of the Cognition and Brain Sciences Unit in Cambridge now think that it is much more localised and at the front of the brain in particular.
Duncan and his team have attempted to link intelligence to the activity of nerve cells in the brain by giving subjects a series of problem solving tests. These tests are of the standard sort used to test and measure intelligence. They resemble puzzles where sequences of numbers or letters have to be rearranged or continued, or patterns of shapes have to be inverted. While subjects are carrying out these intelligence tasks, their heads are scanned to see where electrical activity and blood flow in the brain are concentrated. It turns out that activity was concentrated in the frontal cortex and so, Duncan and his team presume, intelligence is situated there too.
This new idea has not been met with universal acceptance, however. The usual definition of "intelligence" was set by Charles Spearman 100 years ago. This was the quality that allows some people to be very good at a whole variety of things - music, mathematics, practical problem solving and so on - while others are not. He called this quality general intelligence or the "g" factor for short. It was a contentious idea even at the time but still no-one has come up with a better definition. Nonetheless, because the notion of intelligence is imprecisely defined, the idea that there is a fixed location for intelligence has to be questioned. The questioning comes in an article in the prestigious journal Science, the same edition as Duncan's own article. Yale psychologist Robert Stemberg points out that many people, who are clearly intelligent, such as leading politicians and lawyers, do very badly in intelligence tests. Conversely, one might argue, there are plenty of academics who are good at intelligence tests but who cannot even tie their own shoe laces! Sternberg implies that the idea, that being a successful politician or lawyer does not require intelligence, flies in the face of reason. Rather more likely is the idea that so-called intelligence tests can have little to do with many practical manifestations of intelligence. The skills of verbal and mathematical analysis measured by these tests can tell us very little about the skills of social interaction and people handling which are equally essential for success and are, therefore, equally valid qualities of intelligence.
Sternberg makes a further criticism of the conclusions drawn by Duncan's team. The mental-atlas approach really does not tell us anything about intelligence. The fact that we know a computer's "intelligence" is produced by a computer chip and that we can say where this chip is, does not tell us anything about the computer's intelligence or ability. We could easily move the location of the chip and this would not change the computer's "intelligence". As Benjamin Martin points out, this may be what happens in reality when following physical damage to one area of the brain, knowledge and ability appear able to relocate.