Language-like statistical structure arises in learned signaling: evidence from birdsong

All languages have statistically coherent subsequences (e.g., words) whose frequency distribution follows a power law. These properties facilitate language learning in humans, making them good candidates for arising through cultural transmission as a way to help faithful transmission across generations. Recently, both properties were found in whale song, which is also culturally transmitted, leading to the strong prediction that they should be found wherever complex sequential signaling is culturally transmitted. Here, we use the same tools used to analyze human data and whale song to reveal that culturally transmitted Bengalese finch song also has statistically coherent subsequences whose distribution follows a power law. We additionally show that statistical coherence increases over development, but the power law is present throughout, suggesting that it reflects a fundamental principle of learned representations. Finding these parallels between evolutionarily distant species illustrates the importance of cultural transmission in shaping communication and suggests that core properties of language arise through convergent evolution.