Rhythmic Communication Across Species: The 2 Hertz Tempo
A groundbreaking study reveals that diverse animal species—from insects to mammals—share a common communication tempo of roughly two beats per second, likely rooted in the biology of the brain itself.
Research Findings
Researchers from Northwestern University, in collaboration with the University of Geneva, the University of Pennsylvania, and other institutions, analyzed previously published studies and sound recordings of animal communication. The analysis examined rhythmic signals including firefly flashes, cricket chirps, frog calls, bird mating displays, and vocalizations and gestures from mammals.
The study found that many species repeat their communication signals within a narrow range of roughly 0.5 to 4 hertz, despite significant differences in body size, habitat, and communication method. One analysis of over 2,000 sound recordings from 98 animal species found that 95% of those species vocalized at a rate between 0.45 and 4.99 events per second, with a concentration around 2.8 hertz.
Proposed Explanation
The researchers propose that this common tempo may reflect a biological constraint in neural processing. They suggest that animal brains, including human brains, may be naturally tuned to process signals arriving at this pace. Computer models of simple neural circuits built by the research team reportedly responded most strongly to signals within the observed 2–3 hertz range.
According to the researchers, neurons require time to integrate information before firing again, which could cause neural circuits to respond most strongly to signals arriving every few hundred milliseconds. The study suggests that communication signals may have evolved to match the rhythms that brains process most efficiently.
Researcher Statements
"There seems to be an abundance of organisms signaling or communicating at a relatively narrow band of tempos. They all seem to stay around 2 or maybe 3 hertz."
— Guy Amichay, mathematician at Northwestern University and lead author
"We suspect that getting the 'carrier' signal in the right tempo range is key to communicating efficiently. It might not be that the tempo itself conveys any information, but it just serves as a baseline for getting attention."
— Daniel M. Abrams, study senior author and engineer at Northwestern University
Researcher Vijay Balasubramanian of the University of Pennsylvania noted that the biophysics of a single neuron aligns with these rhythms.
Background and Context
The study originated from observations of firefly swarms in Thailand, where researchers noticed firefly flashes and cricket chirps occurred at similar tempos. Further analysis confirmed the species were not synchronizing with each other but sending independent signals at very similar tempos.
The researchers noted that the 2 hertz tempo corresponds to 120 beats per minute, a common tempo in popular music. They also observed that human walking rhythm is roughly 2 hertz. The findings suggest that human perception of rhythms, including beats in music and speech cadence, may arise from the same neural timing principles.
Limitations
The researchers acknowledge that the study analyzed a limited sample of communication types compared to the millions of animal species in existence. They note a potential selection bias, as humans may pay more attention to signals within this frequency range.
"It's tempting to think there's a deeper connection here... But we're still exploring what this might mean."
— Guy Amichay
Study Support
The study was published in the journal PLOS Biology on April 14. It was supported by the Northwestern Institute on Complex Systems (NICO), the Buffett Institute for Global Affairs, the National Institute for Theory and Mathematics in Biology (NITMB), the Swiss National Science Foundation, and other institutions.