'Vocal mimicry hypothesis' falsified? [Part 2]

Figure (a) Ai tapped C4, (b) Ai tapped C5, (c) Time sequence of a test trial.

A few entries ago I uploaded a fragment from a study (Hattori et al., 2013) that discusses an intriguing experiment with three chimpanzees (Pan troglodytes) which were trained to tap regularly on a piano keyboard.

While the video below is convincing, the study reports that only one of the three chimps participating in the experiment was able to do the task: a chimp named Ai (See video).  Furthermore, Ai was only able to synchronize with stimuli at a rate of 600 ms (and not at rates of 400 or 500 ms). In addition, Ai did this in reaction (positive asynchrony) and not in anticipation of the beat (negative asynchrony).

This is similar to what has been found in studies with macaques (Zarco et al., 2009; Konoike et al., 2012) that also seem to opt for a strategy of to react instead of anticipating to a regular beat. All this in contrast with humans that can intentionally synchronize their tapping to various rates (ranging roughly from 200 ms to 1800 ms) of a varying rhythmic stimulus (and not simply a metronome) while showing a negative synchronization error, i.e. in anticipation of the beat.

Another point of a more methodological nature is that the experimentators used, next to sound, what they called 'light navigation' (see diagram above), a visual cue for the chimps to 'remind them' of which key to press. While the authors write "it was unlikely that the visual stimuli affected tapping rhythm by chimpanzees" we can not be sure this is evidence for rhythmic entrainment in the auditory domain.

Nevertheless, with behavioral methods that rely on overt motoric responses it is difficult to separate between the contribution of perception and action (beat perception vs beat production). This makes electrophysiological measures (such as event-related potentials) a more direct and hence attractive alternative. The latter method has been shown a worthwhile, non-invasive alternative in studying cognitive and neural processing in primates (see, e.g., Ueno et al., 2009) and it was used recently in a study probing beat perception in macaques (Honing, Merchant et al., 2012).*

And lastly, these and earlier observations have lead to the auditory timing dissociation hypothesis (Honing, Merchant et al., 2012). This hypothesis accommodates the fact that nonhuman primates performance is comparable to humans in single interval tasks (such as interval reproduction, categorization and interception), but differs substantively in multiple interval tasks (such as rhythmic entrainment, synchronization and continuation).

* N.B. We are eager to collaborate with a primate lab that is willing to do such a relatively simple listening experiment using EEG with chimpanzees; Would be great to compare the results we now have for human adults, newborns, and macaques with the perception of Great Apes ! Feel free to email me :-)

Hattori, Y., Tomonaga, M., & Matsuzawa, T. (2013). Spontaneous synchronized tapping to an auditory rhythm in a chimpanzee. Scientific Reports, 3 DOI: 10.1038/srep01566.

Hasegawa, A., Okanoya, K., Hasegawa, T., & Seki, Y. (2011). Rhythmic synchronization tapping to an audio–visual metronome in budgerigars Scientific Reports, 1 DOI: 10.1038/srep00120

Honing, H., Merchant, H., Háden, G., Prado, L., & Bartolo, R. (2012). Rhesus Monkeys (Macaca mulatta) detect rhythmic groups in music, but not the beat. PLoS ONE, 7 (12) DOI: 10.1371/journal.pone.0051369

Thrirty-two metronomes synchronizing?

If you place 32 metronomes on a static object and set them rocking out of phase with one another, they will remain that way indefinitely. Place them on a moveable surface, however, and something very interesting happens (dedicated to Christiaan Huygens):



For more 'variations' see the Ikeguchi Lab, Japan.

Are monkeys capable of rhythmic entrainment?

Hugo Merchant Lab

On Friday 24 May 2013  Hugo Merchant (Institute of Neurobiology, Querétaro, Mexico) will give a CSCA Lecture with the title Neurophysiology of temporal and sequential processing during a synchronization-continuation tapping task. He will present a recent study investigating rhythmic entrainment in Rhesus monkeys (Macaca mulatta).

A recent study has shown that Japanese macaques (Macaca fuscata) are able to spontaneously synchronize their arm movements when they are paired and facing each other, suggesting that monkeys can coordinate their actions in a social setting and establish some level of rhythmic entrainment (Nagasaka et al., 2013; see earlier entry). However, the asynchronies between the pairs of tapping monkeys are positive, largely dependent on the visual input that the other monkey provides, and with little influence on the sounds that the monkeys made when tapping. The question remains of whether more closer human relatives such as the great apes, show a more sophisticated ability for rhythmic entrainment than macaques.

Macaca mulatta

Hugo Merchant will present a recent study in which two monkeys (Macaca mulatta) were trained in a synchronization-continuation tapping paradigm called a synchronization-continuation tapping task (SCT) in which auditory (A) or visual (V) cues were presented to construct the periodic target interval ranging from 0.45 to 1 second. Initially, animals synchronized their arm movements with a sensory cue by tapping on a push-button, followed by self-pacing of the target interval when the metronome was switched-off. In addition, the monkeys performed a single interval reproduction task (SIRT). We recorded the single-cell activity of 1500 neurons from the macaque medial premotor cortex (MPC) during the task performance.

The results suggest that distinct populations of cells in the MPC can encode different temporal and sequential aspects of the SCT and suggest that MPC is part of a core timing network that uses interval tuning as a signal to represent temporal processing in a variety of behavioral contexts where time is explicitly quantified.

Location: room DS.02, REC D, Nieuwe Achtergracht 129 (entrance through REC G, Nieuwe Prinsengracht 130), Amsterdam.

Time: 16:00 - 17:00 hrs, followed by informal drinks. Registration is not necessary.

For more information, see the website of the CSCA.

Nagasaka, Y., Chao, Z., Hasegawa, N., Notoya, T., & Fujii, N. (2013). Spontaneous synchronization of arm motion between Japanese macaques Scientific Reports, 3 DOI: 10.1038/srep01151

Interested in a PhD position at the University of Amsterdam?

The Institute for Logic, Language and Computation (ILLC) currently has two PhD fellowships available at the Faculty of Science starting on 1 September 2013. Applications are invited from excellent candidates wishing to conduct research in an area in which either the Logic and Language group or the Language and Computation group at ILLC are active, such as the computational modeling of human information processing, especially natural language and music (LaCo) and/or foundational issues in mathematics and computer science (LoCo). For more information, see here. Deadline for applications is 12 May 2013.