Humans aren’t the only animals known to move to a musical beat.
For instance, parrots do it, too. Now rats can be observed. Bopping their headsResearchers report on November 11th insynchronized with the music by Lady Gaga and Mozart. Science Advances.
What’s more, the animals seem to respond to the same tempos that get humans’ feet tapping. The study could help reveal the evolutionary foundations of humans’ sense of rhythm.
“Some of us believe that music is very special to human culture. But I believe that its origin is somehow inherited from our progenitors,” says Hirokazu Takahashi, a mechanical engineer at the University of Tokyo, who studies how the brain works.
The ability to recognize the beat of a song and synchronize the movements of one’s body to it is known as beat synchronization. It’s a mystery why some species, like humans and ParrotsSome people have an innate ability while others don’t (SN: 4/30/09).
For rats in the lab, Takahashi and his colleagues put on Mozart’s “Sonata for Two Pianos in D Major” (K. 448). The team sped up and slowed the tempo, as well as played it at its normal speed, observing the rats’ motions not only visually, but also with wireless accelerometers, which were surgically placed on the rats.
Initial research suggested that the team might have been wrong to believe that body size could determine the tempos that trigger head bopping. Humans tend to prefer foot tapping to music that’s between 120 to 140 beats per minute, but a small animal like a rat would probably need a quicker tempo to get that same reaction, the researchers hypothesized.
“There’s lots of reasons to think maybe [rats]Would prefer quicker rhythms. But that’s not what they found. And that’s intriguing,” says Aniruddh Patel, a psychologist at Tufts University in Medford, Mass., who was not involved in this research. He studies music cognition, which is the brain’s ability to perceive and respond to music.
In the video recordings, the rats’ head bobbing was more pronounced when the sonata played at its usual tempo, around 132 beats per minute. Twenty people listening through headphones equipped with accelerometers found the same results.
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Both humans and rats had a consistent head bopping rate of 120 to 140 bpm. Head bopping was not affected by the speed of the music. Takahashi suggests that this indicates something fundamental about the brains of animals, which is wired to respond rhythmically.
The team also played some of their favorite pop songs for the rats, including Lady Gaga’s “Born This Way” and Michael Jackson’s “Beat It,” and saw a similar response.
Patel acknowledges that rats like beats more than humans, but he doubts that they can synchronize to beats as well as humans.
“I think that that study actually raises more questions than answers in some sense,” Patel says. Parrots and humans show beat synchroicity by performing big, voluntary movements such as head bobbing, dancing, or foot tapping. Special devices were required to capture tiny movements such as head-mounted accelerometers and motion capture technology.
It was easier to observe the behavior when researchers lured the rats into standing on their backs with their water bottles up high.
“The fundamental nature of beat perception and synchronization is that you predict the timing of the beat and you move predictably” he says. “So, we land right on beat or a little ahead of it.” Since the rats’ movements are so tiny, it’s not clear if rats can predict the beats or if they’re just reacting to it.
Takahashi as well as Patel insist that the study is valid. NotResearch shows that rats love to dance to human music. “Music stimulus is very appealing to the brain,” Takahashi says. “But it is not evidence [that] they enjoy or they perceive music.”
Takahashi next wants to explore what other aspects music can be shared with rodents, and other animals. “I’d like to maybe reveal how other properties, like melody and harmony, also relate to the dynamics of the brain.”
