Research Highlight: Research Delves into Fruit Flies and Free Will


Reaching into the realm of philosophy, scientists at Scripps Institution of Oceanography at UC San Diego have contributed to a new study that addresses the free will of animals.

George Sugihara and Chih-hao Hsieh of Scripps stepped out of their typical roles as marine scientists to join an international team that used a combination of automated behavior recording and mathematical analyses to show that free will and true spontaneity could exist, at least in fruit flies.

The power to willfully behave differently in identical settings has recently been questioned by neuroscientists. Previous research had shown that flies do not buzz about aimlessly but forage according to a sophisticated search strategy. The new research now suggests that such strategies can arise spontaneously.

“Animals, especially insects, are usually seen as very complex robots which only respond to external stimuli,” said senior author Björn Brembs from the Free University Berlin. “They are said to be input-output devices. When scientists observe animals responding differently, even to the same external stimuli, they attribute this variability to random errors in a complex brain.”

Brembs and his colleagues developed a novel experiment in which the flight paths of flies were monitored in a completely featureless environment. The researchers tethered fruit flies in completely uniform white surroundings and recorded their turning behavior. The flies did not receive any visual cues from the environment and since they were fixed in space, their turning attempts had no effect.

Results of the experiments failed to yield any meaningful results until they were processed with methods developed by Sugihara and Hsieh to analyze marine ecology data and revealed the origin of the fly’s peculiar spontaneity. The researchers detected a non-linear signature pattern in the fly behavior, one unique to systems whose behavior can be attributed to their design, rather than external forces.

The study was the first that showed that such variability cannot be due to simple random events, nor to a simple stereotyped mechanism, but are generated spontaneously and non-randomly by the brain.

“Our results address the middle ground between simple determinism and randomness that is currently not well understood or characterized,” said Sugihara. “We speculate that if free will exists, it is in this middle ground. This humble experiment addresses the two extreme counter arguments against the existence of free will: That behavior is simply deterministic and that behavior is random. Our measurements show it is neither of these possibilities, which leaves the question an open one.”

The team’s study appeared in the journal PLoS (Public Library of Science) One.

— Mario C. Aguilera

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