It is easy to think of fruit flies as tiny robots that simply respond reflexively to their environment. But just like humans, they take time to collect information and to deliberate when faced with a difficult choice, according to a new study.
The findings, published in the journal Science, could help researchers study cognitive development and defects in humans.
Scientists have long been fascinated by decision- making, said an author of the study, Dr. Gero Miesenbock, a neuroscientist at the University of Oxford.
“Going back to the 19th century, psychologists have measured how long it takes humans to make up their minds,” he said. “Usually if you give people a hard perceptual choice, they take longer, because the brain needs to integrate information until it has enough to make a decision.
“This is the first time in an animal as low as a fruit fly we have been able to show that similar processes occur.”
To study how flies make up their minds, Oxford researchers placed the animals in bifurcated chambers filled on both sides with an odor they had been taught to avoid. When the odor was clearly more potent on one side of the chamber than the other, the flies were quick to choose which chamber to inhabit (and nearly always chose the less odorous one).
But when the difference between chambers was subtle, the flies took longer to make a decision, and were more apt to make the wrong choice.
“We were surprised,” Miesenbock said. “The original thought was that the flies would just act impulsively, they won’t take time to deliberate. We found that’s not true.”
The process so closely mimics decision-making in humans, the researchers said, that the same mathematical models used to describe the actions of deliberating people can be used to predict a fly’s behavior.
The common link between fly and human mental activity appears to be FOXP, a gene that is closely associated with cognitive development and language in humans. Flies with a defective copy of FOXP were found to take much longer making up their minds, the researchers said. Defects in human versions of FOXP have been linked to low intelligence and difficulties with language.
Shamik DasGupta, an Oxford neuroscientist who was the study’s lead author, compared making a decision with a defective version of FOXP to trying to collect water in a leaky bucket. Before making decisions, brain circuits will gather information the way a bucket collects water. In healthy brains, a decision is made when the amount of information reaches a certain level. But when FOXP is defective, “either the flow of information into the bucket is reduced to a trickle, or the bucket has sprung a leak,” he wrote in an article on the lab’s website.
Precisely what role FOXP plays in the various mental processes to which it has been linked — movement, thought, communication, decision-making — remains a mystery, Miesenbock said.
“One factor that’s common to all these processes is they occur as sequences over time,” Miesenbock said. “So perhaps what FOXP does is configures brain circuits to be able to process sequences of information.”
Michael Frank, a neuroscientist at Brown University who was not involved in the study, called it “intriguing” that FOXP might be implicated in the same tasks in flies as in humans. One question raised by the research, he said, is whether the defective gene would affect a fly’s ability to gather information through other senses.
“Could it extend to all domains of cognition and motor control, or is it really specific to this particular kind of task?” he asked.
At the very least, though, the new research suggests that opposable thumbs are not a prerequisite for hand-wringing.
“We now know that cognitive abilities are found very low on the evolutionary tree,” Miesenbock said.