Sensorimotor synchronization to rhythm in an experienced sea lion rivals that of humans.

Is human beat keeping unique among vertebrates? The only non-human data showing consistent and lagless beat matching to novel stimuli, including music, come from Ronan, a trained sea lion [Cook et al., J. Comp. Psychol., 127(4):412-427]. Ronan's convincing demonstration of adaptive auditory-motoric entrainment at age 3 years showed stronger tempo-phase relationships and higher variability than reported in similar studies of human subjects. This apparent performance mismatch has been used to suggest the mechanisms underlying her beat keeping ability are not isomorphic with those of humans. However, in the twelve years since our original report, Ronan has continued intermittent beat-keeping practice. Comparative arguments should consider her improved performance with increased experience and evaluate her ability against human subjects performing similar rhythmic tasks. Here, we report Ronan's contemporary ability to synchronize head movements with novel metronomic sounds presented at novel tempos. We also provide data for ten humans moving in time to the same stimuli using a comfortable arm motion with similar amplitude. This sea lion's sensorimotor synchronization was precise, consistent, and indistinguishable from or superior to that of typical adults. These findings challenge claims of unique neurobiological adaptations for beat keeping in humans.