Scientists typically describe intelligence as consisting of two distinct components: fluid intelligence and crystallized intelligence. Fluid intelligence refers to the general ability to solve new problems and recognize unfamiliar patterns. Crystallized intelligence, by contrast, consists of particular kinds of knowledge.
When children learn to count, for instance, they show gains on crystallized intelligence, even as their fluid intelligence remains constant. Scientists have typically regarded fluid intelligence as the aspect of our thinking that is most determined by genetics, since it can't be easily taught.
And yet these schoolchildren showed gains in fluid intelligence roughly equal to five IQ points after one month of training. The IQs of 68.2% of the populace fall within a 30-point range, so this is a significant change. These kids weren't learning facts they would soon forget. They were learning how to think better.
These improvements were triggered by a mental exercise known as the n-back task. The exercise is not fun, even when translated into videogame format. It begins with the presentation of a visual cue. For the kids in the experiment, the cue was the precise location of a cartoon character.
In the next round, the cue is altered—the cartoon character has moved to a new location. The job of the child is to press the space bar whenever the character returns to a spot where it has previously been, and to ignore the other irrelevant locations. As the children advance in the task, these locations move further back in time, forcing them to sort through an increasing amount of information.
How does this tedious exercise boost intelligence? The crucial change concerned the nature of the children's attention. After repeatedly playing the n-back game, the young subjects were better able to focus on the necessary facts. As a result, they squandered less short-term memory on irrelevant details, such as cartoon locations they didn't need to recall. The children "got better at separating the wheat from the chaff across a variety of different tasks," says John Jonides, a senior author on the paper.