A new study has profound implications for understanding free will, reports Roger Highfield

Even tiny fruit flies may have something akin to free will, according to a remarkable study that adds a new twist to a problem that has perpelexed philosophers for millennia.

	Researchers tethered fruit flies in completely uniform white surroundings and recorded their moves

Some of the greatest thinkers, such as Thomas Hobbes and David Hume have wrestled with the issue of free will, which has a range of scientific, religious, legal and ethical implications and is central to what it means to be human.

Now evidence of spontaneity - a measure of self determination or free will - has been found in Drosophila, the tiny buzzing specks which, over the years, have become one of the favourite experimental subjects of geneticists around the planet.

It had been thought that they simply behave like tiny chemical machines, being attracted by the smell of rotting fruit, and evading being swatted, without giving what they are doing a single thought.

But that underplays the subtlety of the fly mind, according to a study published in the the journal PLoS ONE in which an international team argues that the term 'will' would not apply if our actions were completely random, nor would it be 'free' if they were entirely determined.

So if there is free will, it must be somewhere between chance and necessity - which is exactly where fly behaviour comes to be, according to Björn Brembs from the Free University Berlin.

"Animals and especially insects are usually seen as complex robots which only respond to external stimuli," says Brembs. When scientists observe the flies deviating from the expected response, "they attribute this variability to random errors in a complex brain."

By combining an automatic way to measure fly behaviour, and then using sophisticated mathematical analyses, the international team of researchers showed for the first time that such variability cannot be due to simple truly random events but is generated non-randomly by the brain, so there is an underlying pattern of spontaneity. "We show free will "can" exist, but we do not "prove" it does," said Brembs.

Chaos theory is analogous to what they found, he said, where simple so called "deterministic" equations can produce apparently random behaviour, showing that there is an underlying mathematical logic to the supposed mayhem. And the find refutes claims "that in principle we can built a "Mr. Puppet" whose behaviour we can predict to "95%"" he said.

This also means that a murderer is indeed responsible for his actions and not a puppet driven by his neurochemistry. "If humans brains possessed a similar spontaneity trait, every situation would provide them with several behavioural options. In this sense, a murderer can usually be made responsible for his crimes because he only rarely would be left without alternative."

"The point here is that the people claiming that free will doesn't exist say that one day we will be able to show exactly why a murderer must necessarily have acted the way he did by looking closely at his brain. We can show that you cannot even do this in fly brains, as a matter of principle."

These 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 nonrandom spontaneity if given the chance."

For their experiments, the researchers tethered fruit flies in completely uniform white surroundings and recorded their moves. Given that every direction looks the same to the fly, the team expected them to randomly buzz about. However, the analysis showed that fly behaviour was very different from random noise.

Only after the team analyzed the buzzing flies with methods developed by co-authors George Sugihara and Chih-hao Hsieh from the Scripps Institution of Oceanography in San Diego did they realize the origin of the fly's peculiar spontaneity. "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" said Sugihara.

The reason that fruit flies have this trait is to make them more unpredictable to help them to survive and thrive. "The literature is full of examples of how advantageous unpredictable behaviour is, only one of them being unpredictable escape maneuvers when a prey is chased by a predator," says Brembs.

The team now plans to use genetics to pinpoint and understand the brain circuits responsible for spontaneity. This step could lead directly to the development of robots with the capacity to make their own choices and may given insights into disorders such as depression, schizophrenia or obsessive compulsive disorder, which affects the ability to be spontaneous.

Michelle Thew, chief executive of the British Union for the Abolition of Vivisection, said: "Animals across the spectrum are increasingly being shown to be more intelligent than previously assumed. We would expect to see a corresponding shift in the way they are treated by both science and society as more knowledge emerges."