Rats have a human-like sense of rhythm and can bop their heads in time to musical beats, a new study suggests.
The research, published last week in the journal Science Advances, found that rats have innate beat synchronization. This ability stems from the speed that their brains respond to stimuli, also known as the time constant in the brain.
Scientists long thought this skill was unique to humans, with only a few animals—notably cockatoos—organically busting a move to a tune. This paper, however, represents one of the first scientific inquiries on animals’ sense of rhythm, writes the Guardian’s Hannah Devlin.
“Rats displayed innate—that is, without any training or prior exposure to music—beat synchronization,” says Hirokazu Takahashi, an engineer at the University of Tokyo in Japan and study co-author, in a press release. “Music exerts a strong appeal to the brain and has profound effects on emotion and cognition.”
In the study, researchers measured the head movements of ten rats. By placing small, wireless accelerometers on their rodent participants, the team recorded motions that were imperceptible to the eye. They then played the rats one-minute snippets of Mozart’s Sonata for Two Pianos in D Major at four different tempos ranging from 75 percent to 400 percent of the song’s original speed. The rats also listened to Lady Gaga’s “Born This Way,” Queen’s “Another One Bites the Dust,” Michael Jackson’s “Beat It” and Maroon 5’s “Sugar.”
Twenty human participants also listened to the same songs. They went into a soundproof room and listened to the music through headphones that had accelerometers attached to them. The rats were placed in a dim-lit box and played the music through a speaker.
The researchers wanted to find out which tempo the rats would be most synchronized with, and how that compared to the humans. One hypothesis supposed that the rats’ physical characteristics, such as their quick heartbeats and breathing rates, would mean their optimal music tempo would be faster than ours. Another speculated that the time constant of the brain, which is similar in rats and humans, would dictate the optimal tempo.
The rats moved in time with the music most distinctly when the song’s tempo was 120 to 140 beats per minute—the same range as humans. As the music’s tempo increased, the level of head jerking dropped, as neither the rats nor humans could keep up with the fast pace. The fact that the humans and rats responded to the music in similar ways highlights that they both processed music in the brain as opposed to the body, according to the study.
“This is the kind of work that needs to be done if we are going to uncover the vast abilities that other species have to connect with the world that we’re not yet aware of,” Nina Kraus, a neurobiologist at Northwestern University who wasn’t involved in the study, tells the Wall Street Journal’s Aylin Woodward.
Henkjan Honing, a musical scholar at the University of Amsterdam in the Netherlands who also wasn’t involved in the study, does not agree with its methodology, telling the Wall Street Journal that the rats may have only moved their heads because the music startled them. Researchers would have to demonstrate the animals’ ability to anticipate the beat, rather than simply respond to it, in order to prove the rats exhibit beat synchronization, Honing tells the Wall Street Journal. “It should sort of be slightly early and a bit predictive,” he tells the publication of the rats’ head movements.
Future research on the rhythmic abilities of humans compared to animals may also serve as a window into how music and dancing originated, the researchers write in the paper.
“Next, I would like to reveal how other musical properties such as melody and harmony relate to the dynamics of the brain,” Takahashi says in the press release. “I am also interested in how, why and what mechanisms of the brain create human cultural fields such as fine art, music, science, technology and religion. I believe that this question is the key to understand how the brain works and develop the next-generation A.I.”