Fly Moves: Insects buzz about in organized abandon
Bruce Bower
Flies
aren't deep thinkers. Yet these humble creatures display a penchant for
spontaneous behavior that represents an evolutionary building block of
voluntary choice, also known as free will, a controversial new study
suggests.
By mathematically analyzing flight maneuvers, a team of
scientists showed for the first time that fruit flies move in a way
that is neither wholly random nor predetermined. An evolved brain
mechanism in the fly must generate spontaneous, unpredictable flight
shifts to aid in vital tasks such as avoiding predators and tracking
potential mates, conclude neuroscientist Björn Brembs of the Free
University of Berlin and his colleagues.
"Our results provide strong evidence that the exact prediction
of an individual [fly]'s behavior is impossible," Brembs says. This
finding dovetails with other evidence that people must have a neural
ability to generate spontaneous behavior. Without such an ability,
"it's hard to imagine people having access to free will," he adds.
The researchers reject the traditional assumption that flies
and other animals search for food and engage in other critical
behaviors primarily by using their senses to glean clues from their
surroundings. Instead, the new results suggest that circuitous foraging
routes and other behavioral signatures of flies arise spontaneously,
although sensory clues may also play a role. Brembs' team describes its
findings in the May PLoS ONE.
The researchers placed a drop of glue between the head and
thorax of a fly to attach it to a hook inside an experimental chamber.
Each of the 13 flies tethered in this way could still beat its wings
and move its body. Uniformly white surroundings offered no visual
feedback to the animal. A special device recorded the timing and
magnitude of each fly's movements.
In this barren environment, the flies rarely stayed still and
frequently changed direction. Mathematical methods developed by study
coauthors George Sugihara and Chih-hao Hsieh, both of the University of
California, San Diego, indicated that flies' spontaneous flight
maneuvers were neither totally random nor completely regular or
repetitive. Instead, they had a structured variability that
mathematicians describe as fractal order.
Brembs plans to identify brain areas responsible for flies' spontaneous movements.
At least part of the so-called default network in people's
brains generates spontaneous behavior according to rules similar to
those operating in flies, Brembs speculates. The default network
exhibits spontaneous activity in people at rest (SN: 5/5/07, p. 276:
Available to subscribers at http://www.sciencenews.org/articles/20070505/fob4.asp).
Neuroscientist Randolf Menzel, a bee researcher also based at
the Free University of Berlin, suspects that the brain stimulates
spontaneous behavior in flies and other insects as one way of producing
decision options from which the animal automatically makes a choice.
Brembs' results bear no relation to the concept of free will, Menzel
holds.
Psychologist David L. Gilden of the University of Texas at
Austin also sees no reason to connect Brembs' results to free will.
Flies' spontaneous behavior resembles the fractal structure of many
biological and physical systems poised between stability and chaos,
Gilden notes. These systems include traffic flow, quasar emissions, and
people's memory for time and spatial intervals.
Fractal organization endows a system with the flexibility to
change and adapt to new circumstances, Gilden theorizes. "This issue
goes way beyond biology," he says.
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References: Maye, A. . . . and B. Brembs. 2007. Order in spontaneous behavior. PLoS ONE 2(May):e443. Available at http://dx.doi.org/10.1371/journal.pone.0000443.
Further Readings: Bower, B. 2007. Automatic networking: Brain systems charge up in unconscious monkeys. Science News 171(May 5):276. Available to subscribers at http://www.sciencenews.org/articles/20070505/fob4.asp.
For a multimedia presentation about this research, go to http://brembs.net/spontaneous/.
Sources: Björn Brembs Freie Universität Berlin Institut für Biologie-Neurobiologie 14195 Berlin Germany
David L. Gilden University of Texas, Austin Department of Psychology Center for Perceotual Systems 1 University Station A8000 Austn, TX 78712
Randolf Menzel Freie Universität Berlin Institut für Biologie-Neurobiologie 14195 Berlin Germany
Chih-hao Hsieh Scripps Institution of Oceanography University of California, San Diego La Jolla, CA 92093-0202
George Sugihara Scripps Institution of Oceanography 9500 Gilman Drive University of California, San Diego La Jolla, CA 92093-0225
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