I fly, therefore I am...

Free will and true spontaneity – not the first thing you might think of when considering the common fruit fly. Well, one group of scientists think that we are not giving them enough credit.

They might fly continuously into the same window - but they can do it spontaneously

“Animals and especially insects are usually seen as complex robots which only respond to external stimuli,” said Björn Brembs, senior author on a study published in PLos ONE. “When scientists observe animals responding differently even to the same external stimuli, they attribute this variability to random errors in a complex brain.”

However, using a combination of automated behaviour recording and sophisticated mathematical analyses, an international team of researchers say they have shown for the first time that such variability cannot be due to simple random events - but is generated spontaneously and non-randomly by the brain.

Unsurprisingly, the results caught computer scientist and lead author Alexander Maye from the University of Hamburg by surprise: “I would have never guessed that simple flies who otherwise keep bouncing off the same window have the capacity for non-random spontaneity if given the chance.”

The researchers tethered fruit flies (Drosophila melanogaster) in completely uniform white surroundings and recorded their turning behaviour. In this setup, the flies do not receive any visual cues from the environment and since they are fixed in space, their turning attempts have no effect. Thus lacking any input, their behaviour should resemble random noise, similar to a radio tuned between stations. However, the analysis showed that the temporal structure of fly behaviour is very different from random noise.

The researchers then tested a plethora of increasingly complex random computer models, all of which failed to adequately model fly behaviour.

Only after the team analysed the fly behaviour with methods developed by co-authors George Sugihara and Chih-hao Hsieh from the Scripps Institution of Oceanography at UC San Diego did they realise the origin of the fly’s peculiar spontaneity. “We found that there must be an evolved function in the fly brain which leads to spontaneous variations in fly behaviour” Sugihara said. “The results of our analysis indicate a mechanism which might be common to many other animals and could form the biological foundation for what we experience as free will”.

The next step will be to use genetics to localise and understand the brain circuits responsible for the spontaneous behaviour.