A feel for the groove isn't restricted to humans, but it does seem pretty limited across the animal kingdom. Chimpanzees can keep a beat, but their ability to do so is low compared to Homo sapiens. One species of lemur is better.
A 16-year-old California sea lion (Zalophus californianus) named Ronan blows them all out of the water – even some humans. A new study shows that her ability to bop along to a rhythm isn't just a learned response to some tempos: she can synchronize her movements with new rhythms, suggesting that, once she was trained in what to do, she could adapt and keep a beat to multiple tempos.
"She is incredibly precise, with variability of only about a tenth of an eyeblink from cycle to cycle," says comparative neuroscientist Peter Cook of the University of California Santa Cruz and New College of Florida.
"Sometimes, she might hit the beat five milliseconds early, sometimes she might hit it 10 milliseconds late. But she's basically hitting the rhythmic bullseye over and over and over again."
Ronan, a resident of UC Santa Cruz's Long Marine Laboratory, was the subject of a paper published in 2013 that described her remarkable ability to keep time. At three years of age, when just a juvenile, she was trained to bob her head along with a ticking metronome, and later music, adjusting her beat-keeping as the tempo of the metronome changed.
Later studies questioned whether Ronan's abilities could be as accurate as those of a human, since the initial results showed slightly higher variability in timing than is typically seen in human studies. Other scientists also queried the extensive training Ronan underwent, and whether her time-keeping is the product of the same neurobiological mechanisms as human rhythm.
In the intervening 12 years, Cook and his colleagues occasionally gave Ronan a little practice at the boogie – not much, just 10 to 15 seconds at a time, now and again, for a total of around 2,000 sessions.
"She definitely wasn't overtrained," Cook explains. "Realistically, if you added up the amount of rhythmic exposure Ronan has had since she's been with us, it is probably dwarfed by what a typical one-year-old kid has heard."
Now, as a mature adult, her ability to keep the beat has not only improved – it has outstripped that of some humans. In a follow-up study, the researchers tested Ronan's ability to bop in time with a snare drum tapping at tempos of 112, 120, and 128 beats per minute – the higher and lower of which were tempos to which she had not previously been exposed.
They then tested 10 undergraduate university students with the same sounds, tasking them to keep the beat with movements of their forearms.
"We compared Ronan's performance to that of the adults we tested," the researchers write, "providing the first apples-to-apples comparative assessment of rhythmic entrainment between humans and non-humans with established beatkeeping ability."
Not a single human outperformed Ronan in all of the tests. Her tempo interval, movement interval, and phase-angle – the measures of how close her movements were to the beat – were closer to perfect synchronization than at least some of the humans in all tests. Her time-keeping was noticeably more accurate at faster tempos, too.
At 112, 120, and 128 beats per minute, Ronan's performed average tempo was 113.1, 121.6, and 129.0 beats per minute. The humans' average tempos for the same were 112.4, 119.3, and 126.2, respectively.
The results suggest that non-human animals can be trained to keep a rhythm, if they feel motivated to do so. Many of them probably have little reason to do so in the wild, but doing it in a lab where treats and praise are dispensed can help scientists understand animal intelligence and the way they process information, particularly as they grow into adults.
"One of the most important outcomes of the study is the fact that maturation and experience matter," says animal behaviorist Colleen Reichmuth of UC Santa Cruz. " It's not just a test of rhythmic performance. It reflects her cognitive behavior and her ability to remember and refine it over time."
It's important to note that Ronan was well rewarded for her participation in the study: "When the test session was complete, human participants were thanked and given further details on the nature of the study. Ronan received a toy filled with fish and ice."
The research has been published in Scientific Reports.