Saturday, March 30, 2013

Synchronizing Chimps?

In my thinking about music I have emphasized the simple fact that it involves close synchronization with others. As such synchrony seems neurally simple–fireflies can do it, and spectacularly–the apparent face that we can do it while our close primate relatives apparently cannot is something of a puzzle. My thinking on this goes back to the late 1970s and the work of William S. Condon, a pioneering researcher of interactional synchrony among humans. Condon argued that humans and fireflies were unique in this ability, and that's the position I took in Beethoven's Anvil: Music in Mind and Culture.

However, YouTube videos have revealed that song birds have this ability as well. And now researchers at Kyoto University have done study that demonstrates synchronizing ability in a single chimpanzee, although the study is a bit difficult to follow. Three chimpanzees were tested on their ability tap a steady rhythm on a keyboard. While they were doing this they would also, under some conditions, hear a steady tapping pulse at the same time. One of the three chimps, Ai, spontaneously synchronized her tapping to the pulse while the others seemed to ignore the sound. Ai was also the oldest and most experienced of the three.

However, several questions about behavioral synchrony in chimpanzees arise from current experiment. For example, we did not find flexible alignment of Ai's tapping to other auditory rhythms whereas humans can intentionally synchronize their tapping to various rates in a rage between 200 ms to 1800 ms17. Additionally, Ai's accuracy of tapping was relatively weak and lack of evidence of negative asynchrony makes it unclear whether Ai had clear intention to entrain her movement with auditory rhythms. Moreover, it is also unclear whether Ai's synchronized tapping was truly auditory-motor entrainment because the keyboard produced sound when keys were tapped and it is possible that Ai aligned her sound with auditory stimulus sound. Thus, differences in synchronized tapping between chimpanzees and humans should be clarified extensively in further studies in order to place Ai's synchronized tapping in previous human tapping studies.
The human capacity for synchronization appears to be universal, accurate, and quite intentional. We can turn it on and off and will.

Still these hints from birds and now a single chimp are tantalizing. Perhaps the capacity is lying there in the nervous system, but it is only humans that have managed to tap into it. If so, just how is it that we've been able to do so?

If I had to guess, I'd suspect it has to do with the fact the humans are born earlier in their development than other primates are, and hence are exposed to human-filled external world earlier in life.

See also:

Spontaneous synchronization of arm motion between Japanese macaques

Humans show spontaneous synchronization of movements during social interactions; this coordination has been shown to facilitate smooth communication. Although human studies exploring spontaneous synchronization are increasing in number, little is known about this phenomenon in other species. In this study, we examined spontaneous behavioural synchronization between monkeys in a laboratory setting. Synchronization was quantified by changes in button-pressing behaviour while pairs of monkeys were facing one another. Synchronization between the monkeys was duly observed and it was participant-partner dependent. Further tests confirmed that the speed of button pressing changed to harmonic or sub-harmonic levels in relation to the partner's speed. In addition, the visual information from the partner induced a higher degree of synchronization than auditory information. This study establishes advanced tasks for testing social coordination in monkeys, and illustrates ways in which monkeys coordinate their actions to establish synchronization.

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