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Gone are the days when the term “intelligence” was applied solely to humans. We now speak about intelligent behavior in other species (including plants), and increasingly so in machines. But how much do we know about our own intelligence?
Research into human intelligence is more than a hundred years old. At the early 20th century, it was proposed that general intelligence (one’s mental ability), also known as g, reflects a person’s ability to solve any type of cognitive problem (mathematical, spatial, verbal, etc). The solving of these problems requires recognizing, manipulating and retaining information. Simply put, intelligence is the ability to figure out stuff on the spot and remember it for later use.
Intelligence linked to positive life outcomes
In general, we know that people vary in cognitive ability. These individual differences follow a normal distribution, which means that most people have average intelligence, with relatively few people having very high or very low intelligence. Another well-established finding is that intelligence is strongly related to important life outcomes, such as achievement in school, performance on the job, and one’s health. In fact, people who have higher cognitive ability as children are more likely to live longer.
The cause of the intelligence-longevity relationship is not entirely clear though. Higher-educated individuals have higher-paying jobs, and so they enjoy better living conditions (like access to better food and healthcare) – such would be the environmental explanation. However, a genetic explanation has also been proposed based on a twin study. Researchers assessed the trend for the brighter twin to live longer and found that it was stronger in fraternal (twins who share 50% of their genes) than identical twins, who are genetic copies of each other. If environment rather than genetics has a stronger influence on intelligence and longevity, we would expect this relationship to be stronger in identical twins. Yet the opposite has been observed.
Is there an intelligence gene?
It seems then that genes do matter when it comes to intelligence. Have we been able to identify specific genes that influence intelligence? Well, not really. To-date, scientists have found hundreds of genes that can be linked to cognitive ability, however a large number of them have only a small influence on intelligence. Thus there isn’t an intelligence gene.
Where is the seat of intelligence in the brain?
Quite a similar conclusion can be reached when it comes to brain and intelligence. Research that set out to answer the ‘where is the seat of intelligence?’ question showed that no brain area is per se responsible for cognitive performance. Intelligent behavior arises out of connections between areas in the parietal and frontal lobe – the way these areas are able to exchange information with one another. This means that high intelligence is a product of sending information without disruptions among the involved areas, rather than the way any specific region works.
While we have begun to acknowledge and study intelligence in species beyond our own and even in non-biological entities, we still have a lot to uncover about the biological foundations of human intelligence. By understanding ourselves better, we can perhaps understand the way intelligent behavior emerges in other organisms.