Illustration: Uday Deb

In the list of things we regard as immutable, intelligence would rank very high. We all learn as we go along, and become better at doing many things, but our innate intelligence remains the same. According to conventional wisdom, no amount of training can alter this fact, and most scientists seemed to agree. At least until recently. Now there is evidence to the contrary — that we can improve our intelligence with the right kind of training.

For at least a century scientists have been looking at measuring intelligence, although an absolute and precise method still does not exist. Whether precisely measurable or not, they still thought that a substantial part of intelligence was inherited, and there was general agreement that this part could not be improved by mental training. But now some scientists say that we can improve even what is inherited.

Susanne Jaeggi and her colleagues at the University of Michigan had started work on improving intelligence about three years ago. Jaeggi and her co-worker Martin Buschkuehl had both done their PhDs from the University of Bern in Switzerland. After they moved to the University of Michigan as post-doctoral students, they worked with their former university to develop some mental exercises. They used these exercises to train young adults, and then tested their intelligence. It turns out that those who did the exercises improved their intelligence. “It is like physical training,” says Jaeggi. Those who exercise generally improve their ability in a specific game.

The concept of inherited intelligence is at least four decades old. In the 1960s, the controversial Arthur Jensen, now professor emeritus at the University of California in Berkeley, put forth the concept of a general intelligence factor — which he called g — that is inherited. The controversy was about his ideas on race and IQ, which were widely criticised, but psychologists tended to accept the idea of an inherited intelligence.

In the 1970s, Harvard psychologist Raymond Cattell defined two kinds of intelligence: crystallised and fluid. Crystallised intelligence is the ability to use knowledge and experience. Fluid intelligence is the ability to solve new problems, including abstract reasoning. Crystallised intelligence uses memory and knowledge while fluid intelligence is totally independent of these. Both were thought to be independent neural processes. While crystallised intelligence improves with knowledge and memory, fluid intelligence does not. At least that was the general thinking in the scientific community.

Psychologists had been trying for some time to see whether fluid intelligence improves with training. Several studies have shown that IQ is highly heritable although there were differences with age and social class. Fluid intelligence is generally measured by figure analogies, classification and problems involving matrices. Jaeggi and her colleagues now show, in a paper published in The Proceedings of the National Academy of Sciences, not only that fluid intelligence improves with training but also that the improvement can be carried over to tasks that bear no relationship to the training exercises. Moreover, the more you do these exercises, the more fluid intelligence improves.

The commercial memory improvement market is full of training programmes that claim to improve memory and the brain. “With training it is possible to remember lists of over thousands of items,” says Jaeggi. There are other programmes that claim to improve the brain in general and not just memory. One pioneered by Michael Merzenich of the University of California in San Francisco is based on the theory that our brains decay as we age because we tend to learn new tasks less and less. The aim of this programme is primarily to reverse memory loss while improving general brain fitness.

Jaeggi and the University of Bern used different techniques. The exercises were what psychologists now call “dual -back” tasks, which involved listening and watching a figure at the same time. Then the trainee had to remember and reproduce certain visual stimuli — a series of coloured boxes, for example. The exercises are adaptive. The stimuli gradually increase in complexity.

“As the participants learn to do the tasks well, the complexity of the tasks increases,” says Jaeggi. The participants of the tests were nine students in their early twenties, and all of them showed improvements in their ability to do quite dissimilar tasks.

So what do these results mean? It does not necessarily show that all of intelligence is nurtured and not inherited. It could be that fluid intelligence is strongly inherited, but it also means that one can improve the brains significantly with training. We had already known that crystallised intelligence can be improved with training. Now we know that even fluid intelligence can be improved. This is consistent with what neurobiologists like Merzenich are now showing. The brain is an extremely plastic organ. It can decay if you do not use it, but you can improve it like the way you improve your physique through training. Even in old age.