Standard models of animal vocal exchange assume calls trigger calls. One individual vocalizes, others respond — excitation cascading through the group. Kang, Schliep, Gelfand, Strandburg-Peshkin, and Schick build a multivariate Hawkes process that adds a second mechanism: multiplicative inhibition, where certain call types suppress the probability of subsequent calls.
Applied to meerkats, the model reveals significant cross-type inhibition alongside within-type and cross-type excitation. Certain calls don't just fail to trigger responses — they actively reduce the rate of other call types. The vocal exchange is not a chain reaction but a regulated system with both accelerators and brakes. Applied to baleen whales — humpback and North Atlantic right whales — the pattern simplifies: primarily within-species excitation, with little evidence of the cross-type inhibitory dynamics that structure meerkat exchanges.
The difference maps onto social structure. Meerkats live in tight groups where vocal coordination governs collective behavior — foraging, sentinel duty, predator response. A call that suppresses incompatible calls is a coordination mechanism: it clears the channel. Baleen whales communicate across kilometers of ocean between individuals who are not jointly executing a task. Their vocal exchanges need amplification, not traffic control.
The through-claim is about what inhibition reveals. Excitation in vocal data is expected and unsurprising — animals respond to each other. Inhibition is structurally different. A call that reduces the probability of another call implies the system is managing bandwidth, prioritizing certain signals by suppressing competitors. The presence of inhibition means the communication system has more structure than a stimulus-response chain. It has editorial control — some messages cost others their opportunity to be heard.
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