When people with very high IQs are given moderately difficult task, their brains work more efficiently compared to people with slightly above-average IQs.

To describe the effect, Elsbeth Stern, a professor at ETH Zurich, uses the analogy of a more and less efficient car:

“When both cars are traveling slowly, neither car consumes very much fuel. If the efficient car travels at maximum speed, it also consumes a lot of fuel. At moderate speeds, however, the differences in fuel consumption become significant.”

Scientists refer to this as the neural efficiency hypothesis—although most experts accept it as an undisputed fact.

While working on her doctoral thesis in Stern’s work group, Daniela Nussbaumer found evidence of this effect in a group of people possessing above-average intelligence for tasks involving what is referred to as working memory.

“We measured the electrical activity in the brains of university students, enabling us to identify differences in brain activity between people with slightly above-average and considerably above-average IQs,” says Nussbaumer.

Past studies of neural efficiency have generally used groups of people with extreme variations in intelligence.

EEG Measurements

Psychologists define working intelligence as a person’s ability to associate memories with new information as well as to adapt to changing objectives by filtering out information that has become irrelevant. The frontal lobe plays a pivotal role in these processes.

In order to test these abilities, the researchers asked 80 student volunteers to solve tasks of varying complexity on a computer.

One task, for example, was to determine whether individual letters or faces were part of a selection of letters or faces that had been shown to the subjects immediately beforehand.

An especially difficult task involved identifying letters and faces shown to the subjects during past runs of the test within a time limit. While the students were completing the tests, the researchers used electroencephalography (EEG) to measure their brain activity.

EEG and other brain activity readings are not precise enough to assess the intelligence of an individual. Still, using these methods may be an interesting way to study how different levels of intelligence are manifested in the brain.

Smart vs. Very Smart

For the results analysis, the researchers had the subjects take a conventional IQ test and then split them into two groups: one with slightly above-average IQs and another with well above-average IQs.

The researchers found no differences in brain activity in either group of subjects when they performed very easy or very difficult tasks. They did, however, see clear differences in the case of moderately difficult tasks.

Stern attributes this to the fact that none of the subjects had any trouble whatsoever with the simple tasks and that the difficult tasks were cognitively demanding even for the highly intelligent subjects. In contrast, all subjects succeeded in solving the moderately difficult tasks, but the highly intelligent subjects required fewer resources to do so.

Daniela Nussbaumer, Roland H. Grabner, Elsbeth Stern Neural efficiency in working memory tasks: The impact of task demand Intelligence Volume 50, May–June 2015, Pages 196–208

Photo: subject solves a facial recognition task while EEG measurements of electrical activity in his brain are measured. Photo: Fabio Bergamin/ETH Zurich

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