Song and rhythm learning in songbirds and humans
As music can engage human listeners, birdsong appears to engage bird listeners: but how? In one study we tested how birds synchronize calls and songs to promote social engagement. In a second study we show that musical balance between regularity and novelty can be identified in the signing performances of individual birds. In both studies, similar principles can explain the design of complex vocal communication across a broad range of animal species.
First study: We examined how zebra finches learn to synchronize their calls using vocal robot that exchanges calls with a partner bird. We found that birds quickly learn to synchronize their calls with those of the robot, and avoid disruptive masking (jamming) by adjusting the timing of their responses. Further, when challenged with complex rhythms, birds can dynamically adjust the timing of their calls in anticipation of jamming. Blocking the song system cortical output dramatically reduced the precision of birds’ response timing and abolished their ability to avoid jamming. Findings suggest that descending forebrain projections, including the song-production pathway, function as a general-purpose communication system. In the case of calls, it enables plasticity in vocal timing to facilitate social interactions, whereas in the case of songs, plasticity extends to developmental changes in vocal structure.
Second study: Music maintains a characteristic balance between repetition and novelty. Do individual songbirds strike a balance between the complexity of their repertoire and the temporal regularity of their singing performance? We found, in free-living Australian pied butcherbirds, that different song types often share motifs. These shared motifs reappeared in strikingly regular temporal intervals across different song types, but only in birds of high repertoire complexity. Results suggest that individual birds regulate the temporal diversity of shared motifs in a manner that takes their repertoire complexity into account.
