Rat-hythm and blues: animals show beat synchronization

BioTechniques News
Beatrice Bowlby

In two separate studies, researchers have shown for the first time that rats and seals show innate beat synchronization, which may help understand human musicality.

Have you ever thought that the cute pet rat dancing in the TikTok that everyone shared seemed uncannily rhythmic? Or wondered whether seals naturally move to music? New research suggests that observations of beat synchronization in animals are not coincidental.

Scientists at the University of Tokyo (Japan) have demonstrated for the first time in a scientific study that untrained rats nod their heads in time with music in a comparable manner to humans [1]. In a separate study, researchers from Aarhus University (Denmark) reported that baby seals recognize and respond to variations in the rhythm and tone of seal calls [2]. Both teams of researchers believe that their report of innate beat synchronization in mammals could help unlock the origins of human musicality.

In humans, babies develop innate beat synchronization ­– the ability to recognize, respond to, and even predict rhythm – in tandem with language processing. This complex neurological skill indicates the developing interaction between the auditory and motor systems.

(You make me feel like) A Rat-ural Woman

To examine rats’ natural beat synchronization, the Japanese team of researchers, led by Hirozaku Takahishi, compared the head movements of 10 mice and 20 humans using accelerometers. The team played 1-minute clips from Mozart’s ‘Sonata for Two Pianos’ in D Major, K. 448, varying the tempo from the original 132bpm to assess the participants’ response at different speeds.

The results showed that the rats and humans jerked their heads with comparable rhythms and their beat synchronization was clearest in the same range – 120–140bpm.

“After conducting our research with 20 human participants and 10 rats, our results suggest that the optimal tempo for beat synchronization depends on the time constant in the brain,” said Takahashi. He added that given this is similar across animals, “this demonstrates that the animal brain can be useful in elucidating the perceptual mechanisms of music.”

Whilst researching this effect, the team hypothesized that this ‘beat tuning’ in the brain is the result of short-term adaptations in the auditory cortex. By modelling this change mathematically and comparing it to the neural activity data they collected, the researchers showed that the ability to predict beat is clearest when the gap between beats is around 1/1000th of a second. Given that this is also the average interval between notes in classical music, Takahashi believes that “the adaptation property in the brain underlies the perception and creation of music.”

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Signed, Seal-ed, Delivered

The Danish researchers took a different approach by assessing the response of 20 harbor seal pups to different seal calls. They applied an approach used to study rhythm perception in human babies by counting the number of times seal pups turned their heads to different seal calls with varied rhythms and tempos.

Their results show that seals recognize different calls based on their rhythm and tempo. Senior author Andrea Ravignani said, “Our study represents a significant step forward in relation to our understanding of humankind’s own musicality and language development, about which we still don’t know very much today. By showing that another vocally plastic mammal can also perceive different rhythms, we support the scientific hypothesis that the two abilities are interconnected.”

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The drumbeat of progress?

Both groups of researchers believe that there is more to discover through studying animals’ beat synchronization. Takahashi said, “Next, I would like to reveal how other musical properties such as melody and harmony relate to the dynamics of the brain. 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 AI.”

In the shorter term, he added, “Also, as an engineer, I am interested in the use of music for a happy life.”

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