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  • Richard Conniff writes about behavior, in humans and other animals, on two, four, six, and eight legs, plus the occasional slither.

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Built for Singing Duets

Posted by Richard Conniff on November 4, 2011

That old slogan “A woman needs a man like a fish needs a bicycle” always struck me as not nearly as clever as its admirers seemed to think.  The truth, often annoying, sometimes delightful, is that women and men need each other like a fish needs a school.

Or, maybe, like birds need a flock.  Here’s a new study published yesterday in Science:

Long-married human couples may finish each others’ sentences, but the plain-tailed wrens of the Andes take things a step further. Male and female wrens sing intimate duets in which they alternate syllables so quickly it sounds like a single bird is singing. New research shows that the brains of both the male and female wrens actually process the entire duet, not just each bird’s own contribution. These findings are surprising because researchers have generally assumed that the brain activity of each songbird would be largely devoted to that bird’s own singing role. Eric Fortune and colleagues recorded the wrens as they sang while hiding in the bamboo forests on Ecuador’s Antisana volcano. Analyzing these recordings, the researchers learned that the female birds seem to establish the timing of the song and that males, but not females, make occasional mistakes during singing. Next, the researchers recorded the brain activity in the birds’ song center while playing back recordings of bird duets as well as solos. The brain neurons responded most vigorously to the duets, suggesting that certain brain circuits — which are shared by humans — are primed for cooperation.

And here’s an account of the study from Newswise:

The brain was built for cooperative activity, whether it be dancing on a television reality show, constructing a skyscraper or working in an office, according to a study led by Johns Hopkins behavioral neuroscientist Eric Fortune and published in the Nov. 4 issue of the journal Science.“What we learned is that when it comes to the brain and cooperation, the whole is definitely greater than the sum of its parts,” said Fortune, of the Department of Psychological and Brain Sciences at the university’s Krieger School of Arts and Sciences. “We found that the brain of each individual participant prefers the combined activity over his or her own part.”

In addition to shedding light on ourselves as social and cooperative beings, the results have important implications for engineers who want to be able to program autonomous robots to work effectively as teams in settings such as bomb squads and combat.

But Fortune’s work didn’t involve androids or take place on a battlefield. Instead, he and his team took to the cloud forests of Ecuador, on the slopes of the active Antisana Volcano. Why? It’s one of the only places in the world where you can find plain-tailed wrens. These chubby-breasted rust-and-gray birds, who don’t fly so much as hop and flit through the area’s bamboo thickets, are famous for their unusual duets. Their songs — sung by one male and one female — take an ABCD form, with the male singing the A and C phrases and the female (who seems to be the song leader) singing B and D.

“What’s happening is that the male and female are alternating syllables, though it often sounds like one bird singing alone, very sharply, shrilly and loudly,” explained Fortune, who spent hours hacking through the thick bamboo with a machete, trying to catch the songbirds in nets. “The wrens made an ideal subject to study cooperation because we were easily able to tape-record their singing and then make detailed measurements of the timing and sequences of syllables, and of errors and variability in singing performances.”

The team then captured some of the wrens and monitored activity in the area of their brains that control singing. They expected to find that the brain responded most to the animal’s own singing voice. But that’s not what happened.

“In both males and females, we found that neurons reacted more strongly to the duet song — with both the male and female birds singing — over singing their own parts alone. In fact, the brain’s responses to duet songs were stronger than were responses to any other sound,” he said. “It looked like the brains of wrens are wired to cooperate.”

So it’s clear that nature has equipped the brains of plain-tailed wrens in the Andes of Ecuador to work cooperatively and to prefer “team” activities to solo ones. But what does that have to do with people?

“Brains among vertebrate animals — frogs, cats, fish, bears and even humans — are more similar than most people realize,” Fortune said. “The neurotransmitter systems that control brain activity at the molecular level are nearly identical among all vertebrates and the layout of the brain structures is the same. Thus, the kinds of phenomena that we have described in these wrens is very relevant to the brains of most, if not all, vertebrate species, including us humans.”

CITATION:   “Neural Mechanisms for the Coordination of Duet Singing in Wrens,” by E.S. Fortune; D. Li; G.F. Ball at Johns Hopkins University in Baltimore, MD; E.S. Fortune; C. Rodriguez at Pontificia Universidad Católica del Ecuador in Quito, Ecuador; M.J. Coleman at Claremont McKenna College in Claremont, CA; M.J. Coleman at Pitzer College in Claremont, CA; M.J. Coleman at Scripps College in Claremont, CA.

 

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