Two Wren Brains Are Better Than One

by Brian Kateman | November 7, 2011

When we participate in a balloon toss, dance the tango, or sing a duet, we experience a delightful feeling of unity, a seamless and powerful collective identity. The shared mental space is essential to the success of cooperative behaviors, guiding team members to make decisions and communicate messages that accomplish an objective.

Foraging, mating, reproduction, hunting, parental care, and countless other behaviors are simply less effective when done alone; evolutionarily, the social animal is often the more successful one. Among vertebrates, the brain reflects the advantages and power of two, as demonstrated by behavioral neuroscientist Eric Fortune in the November 4 issue of the journal Science.

As reported by Science Daily, Fortune, of the Department of Psychological and Brain Sciences at the Krieger School of Arts and Sciences, traveled to the cloud forests of Ecuador near Antisana Volcano to study plain-tailed wrens. These so-called bamboo specialists birds are famous for their unusually repetitive and rolling duets. The two-part choruses take an ABCD form, where the male sings the A and C phrases and the female sings the B and D phrases. Fortune and his team tape-recorded the birds’ singing and made detailed measurements of the timing and sequences of the syllables to evaluate the performance.

When the researchers observed activity in the brains of the birds while singing, they discovered something striking: In both sexes, the neurons reacted more strongly to the duet song than individual contributions — they are seemingly wired to enhance cooperation.

As explained by Fortune, the kind of phenomena observed in the plain-tailed wrens is ubiquitous among vertebrates. The brains of frogs, dogs, sharks, monkeys, and even humans are very similar on the molecular level. For many species, emotions like shame, love, guilt, and honor drive cooperative behaviors, uniting a group of individuals to increase their chances of surviving and reproducing.

While debate surrounds the exact mechanism of selection for cooperative behaviors (with David Sloan Wilson and Group Selection in one corner and Richard Dawkins and Gene Selection Theory in the other), the importance of working together is evident, both in our daily lives and in the inner-workings of the vertebrate brain.

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