Fruit flies display rudimentary free will

Fruit flies display rudimentary free will

01:00 16 May 2007
NewScientist.com news service
Bob Holmes

Fruit flies have free will. Even when deprived of any sensory input to react to, the zigs and zags of their flight reveal an intrinsic, non-random - yet still unpredictable - decision-making capacity.

If evolution has furnished humans with a similar capacity, this could help resolve one of the long-standing puzzles of philosophy.

Science assumes that effects have causes, and that if we understand the causes well enough we can predict the effects. But if so, our experience of being free to make choices is an illusion, since we are in effect just sophisticated robots responding to stimuli. If our behaviour is unpredictable, this is only because random events prevent us from responding perfectly to our environment.

To test whether behaviour can be truly random, Björn Brembs, a neurobiologist at the Free University of Berlin in Germany, put fruit flies into a sensory deprivation chamber: a drum with a white interior, that offers the flies no visual cues to orient themselves.

The flies were glued to a torque meter that measured their zigs and zags as they attempted to fly. (Watch a video of a fly in the chamber.)
Non-random behaviour

Brembs and colleagues analysed the resulting flight records using increasingly sophisticated models of random behaviour. Were the flies' decisions random, like the result of a coin flip? No. Did they fit a coin-flip model in which the probability of "heads" varied randomly? Again, no.

Nor could they be explained by a series of random inputs, or a series of random inputs combined in non-random ways.

Instead, the researchers found that the flies' behaviour bears the hallmark of chaos - a non-random process that is nevertheless unpredictable, like the weather. No one has yet been able to adequately explain how chaos arises.
Chaotic advantage

The chaotic control gives flies' flight a spontaneity that might be evolutionarily advantageous when searching for food, say, or when a female tries to avoid an unwanted male. And, unlike true randomness, evolution can fine-tune the level of this spontaneity, Brembs says.

It's a rudimentary sort of free will, he adds. A more sophisticated version of chaotic control could help human will break free of simple, robotic cause and effect.

"It makes a lot of sense to assume that what we experience as free will is based on components that have cropped up in evolution long before," says Brembs.

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