A Common Tempo in Animal Communication

A study published in PLOS Biology on April 14 reports that rhythmic communication signals across a wide range of animal species tend to repeat at a tempo of approximately 2 hertz, or two beats per second. The research, led by scientists from Northwestern University, analyzed existing studies of animal communication and proposes this common tempo may reflect a biological constraint in how neural circuits process information.

Key Findings

• An analysis of previously published research found that many animal species repeat communication signals within a narrow range of roughly 0.5 to 4 hertz, with a clustering around 2 hertz.
• This pattern was observed across diverse species, including fireflies, crickets, frogs, birds, fish, and mammals.
• The signals analyzed included light pulses (e.g., firefly flashes), auditory chirps and calls (e.g., cricket chirps, frog calls), and visual displays (e.g., bird mating dances).
• The common tempo was noted across eight orders of magnitude in body weight and in terrestrial, aerial, and aquatic environments.

Proposed Explanation and Methodology

The researchers propose the observed tempo may align with a fundamental constraint in neural processing. They suggest animal brains, including human brains, may respond most strongly to signals arriving at this pace, making it an efficient rhythm for communication.

To test this idea, the research team built computer models of simple neural circuits. According to their models, these circuits responded most strongly to pulsed signals within the same 2-hertz range observed in the animal communication data. The researchers note this aligns with the biophysics of neurons, which require time—on the order of a few hundred milliseconds—to integrate information before firing again.

Research Origin and Context

The study originated from fieldwork observations of firefly swarms in Thailand, where researchers noted that firefly flashing and independent cricket chirping occurred at similar tempos. This prompted a broader investigation into communication rhythms across species.

The research team included Guy Amichay and Daniel M. Abrams of Northwestern University, and Vijay Balasubramanian of the University of Pennsylvania. Balasubramanian noted that the biophysics of a single neuron operates at similar rhythms.

The researchers also noted that the 2-hertz tempo corresponds to 120 beats per minute, a common tempo found in many rock and pop songs.

Researcher Statements

• Guy Amichay, the study's lead author, stated: "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."
• Daniel M. Abrams, the study's senior author, said: "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."

Study Scope, Support, and Next Steps

The study analyzed 74 communication types across various species. The researchers acknowledge this is a small sample compared to the millions of animal species and note a potential selection bias, as humans may pay more attention to signals within this frequency range.

The research was supported by the Northwestern Institute on Complex Systems (NICO), the Buffett Institute for Global Affairs, and the National Institute for Theory and Mathematics in Biology.

The researchers expressed hope that the study will inspire further investigation, including the examination of more species and direct measurement of brain responses to different communication rhythms. They suggest understanding this tempo could aid in interpreting animal signaling and social behavior, and that human perception of rhythm in music and speech may arise from similar neural timing principles.