If you find it hard to imagine how any such thing could be packed into a brain (hardly more than a tangle of neurons) that small, you are not alone. Scientists have basically viewed insects "as complex robots which only respond to external stimuli," says Björn Brembs of the Free University Berlin. Of course, lots of scientists think this about humans, too, viewing our brains as input-output devices responding to external stimuli, neurochemicals and earlier brain activity in a deterministic way that leaves no room for free will.
Brembs and his colleagues weren't so sure. To investigate whether fruit flies (Drosophila melanogaster) are automatons or not, they tethered flies in a completely uniform, white enclosure. The flies had no visual cues from the environment and are fixed in space. Their behavior should therefore resemble random noise. But a mathematical analysis showed that it did not, and no random computer models successfully modeled the flies' behavior, the scientists report in the open-access journal PloS ONE.
Instead, it exhibited spontaneous variation, which the scientists speculate "might be common to many other animals and could form the biological foundation for what we experience as free will."
This will certainly not dismiss determinists, who can rightly point out that the scientists looked at a fairly high level of behavior "what the flies were doing "rather than a level where determinism might reign, namely, brain activity. Still, more and more neuroscientists are coming around to the idea that human behavior is neither completely random nor entirely determined. "The question of whether or not we have free will appears to be posed the wrong way," says Brembs. "If we ask, 'How close to free will are we?,' one finds that this is precisely where humans and animals differ." Brembs has a cool multimedia version of the experiment at http://brembs.net/spontaneous.