FLIES MAY EXPERIENCE something analogous with human fear when they are being chased by humans holding newspapers.

That is the finding of a new Caltech study that may help humans understand how their own brains are wired.

The study, which was done in the laboratory of David Anderson, Seymour Benzer Professor of Biology and an investigator with the Howard Hughes Medical Institute, was published online in the journal Current Biology.

While they are not as close to humans on the evolutionary scale, their neurological systems are easier to study than mice.

Because researchers know the experience of human emotion, they might anthropomorphise those of an insect — just as you might assume that the shooed-away fly left your plate because it was afraid of your hand.

But there are several problems with such an assumption, says post-doctoral scholar William T Gibson, first author of the paper.

There are two difficulties with taking your own experiences and then saying that maybe these are happening in a fly. First, a fly’s brain is very different from yours, and second, a fly’s evolutionary history is so different from yours that even if you could prove beyond any doubt that flies have emotions, those emotions probably wouldn’t be the same ones that you have.

The researchers broke emotions down to their constituent building blocks or emotion primitives.

Gibson explains by analogy that emotions can be broken down into these emotion primitives much as a secondary color, such as orange, can be separated into two primary colors, yellow and red. “And if we can show that fruit flies display all of these separate but necessary primitives, we then may be able to make the argument that they also have an emotion, like fear.”

In the future, the researchers say that they plan to combine the new technique with genetically based techniques and imaging of brain activity to identify the neural circuitry that underlies these defensive behaviours, but they can’t tell us whether flies are afraid when you try to kill them.

“Our work can get at questions about mechanism and questions about the functional properties of emotion states, but we cannot get at the question of whether or not flies have feelings,” Gibson says.

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