Linguistic law-like compression strategies emerge to maximize coding efficiency in marmoset vocal communication

Human language follows statistical regularities or linguistic laws. For instance, Zipf's law of brevity states that the more frequently a word is used, the shorter it tends to be. All human languages adhere to this word structure. However, it is unclear whether Zipf's law emerged de novo in humans or whether it also exists in the non-linguistic vocal systems of our primate ancestors. Using a vocal conditioning paradigm, we examined the capacity of marmoset monkeys to efficiently encode vocalizations. We observed that marmosets adopted vocal compression strategies at three levels: (i) increasing call rate, (ii) decreasing call duration and (iii) increasing the proportion of short calls. Our results demonstrate that marmosets, when able to freely choose what to vocalize, exhibit vocal statistical regularities consistent with Zipf's law of brevity that go beyond their context-specific natural vocal behaviour. This suggests that linguistic laws emerged in non-linguistic vocal systems in the primate lineage.

Automated summary

Human language follows statistical regularities and linguistic laws, such as the concise Zipf's law. It is unclear whether this law emerged de novo in humans or also exists in the non-linguistic vocal systems of our primate ancestors. Through studying marmoset monkeys, we found that they exhibit vocal statistical regularities consistent with Zipf's law in their vocalizations, suggesting that linguistic laws may have emerged in non-linguistic vocal systems in the primate lineage.