Think before you act!

May 22, 2014

Fruit flies take time to deliberate when faced with difficult decisions. The process is linked to FoxP, a gene associated with cognitive development and language in humans.

Have you ever agonized over a difficult decision? Reflecting before committing to a choice is considered a hallmark of intelligence. In a study published in the journal Science, CNCB researchers report that fruit flies also ‘think’ before they act.

The insects were given choices between two concentrations of an odour. Before the experiment, the flies had been taught to avoid one concentration, which they had learned to associate with a negative outcome. When the odour concentrations were very different (and, therefore, easy to tell apart), the flies made quick decisions which were nearly always correct.

But when the odour concentrations were very close, making them difficult to distinguish, the flies mulled over their choices much longer, and they made more mistakes.

‘Psychologists and neuroscientists have studied these types of perceptual decision in humans and higher vertebrates since the 19th century,’ says Gero Miesenböck, in whose laboratory the new research was performed. ‘But people tended to think of insects as tiny robots that just respond reflexively to signals from the environment. Now we know that’s not true.’

Remarkably, the same mathematical models that describe the actions of a human decision-maker also accurately predict a fly’s behaviour.

The scientists discovered that flies carrying defective copies of a gene called FoxP were much slower to make up their minds. Defects in some human versions of theFoxP gene are associated with low intelligence, difficulties with language, and problems with fine movements.

Shamik DasGupta, the lead author of the study, illustrates the effect of FoxP by comparing the decision process to filling a bucket with water: ‘Before a decision is made, brain circuits collect information just like a bucket collects water. Once the amount of accumulated information has risen to a certain level, the decision is triggered. When FoxP is defective, either the flow of information into the bucket is reduced to a trickle, or the bucket has sprung a leak.’

In an experiment suggesting that the comparison with a leaky bucket is apt, the researchers were able to copy the genetic defect by introducing an electrical current leak into the 200 or so brain cells in which FoxP is active.

What role FoxP genes play in mental processes as diverse as decision-making, language, and motor control remains puzzling. One feature common to all of these processes is that they unfold over time. FoxP may thus be important for wiring into the brain a capacity for producing and processing temporal sequences.

FoxP influences the speed and accuracy of a perceptual decision in Drosophila by Shamik DasGupta, Clara Howcroft Ferreira and Gero Miesenböck. Science (2014) 344: 901–904.

Even Fruit Flies Need a Moment to Think It Over. The New York Times, May 22, 2014.