Recursive sequence generation in monkeys, children, U.S. adults, and native Amazonians

• Published in: Science advances Vol. 6; no. 26; p. eaaz1002
• Main Authors: Ferrigno, Stephen, Cheyette, Samuel J., Piantadosi, Steven T., Cantlon, Jessica F.
• Format: Journal Article
• Language: English
• Published: United States American Association for the Advancement of Science 01.06.2020
• Subjects: Psychological Science; SciAdv r-articles
• ISSN: 2375-2548; 2375-2548
• DOI: 10.1126/sciadv.aaz1002

The ability to represent recursive sequences is early developing and found across cultures, but is not unique to human thought. The question of what computational capacities, if any, differ between humans and nonhuman animals has been at the core of foundational debates in cognitive psychology, anthropology, linguistics, and animal behavior. The capacity to form nested hierarchical representations is hypothesized to be essential to uniquely human thought, but its origins in evolution, development, and culture are controversial. We used a nonlinguistic sequence generation task to test whether subjects generalize sequential groupings of items to a center-embedded, recursive structure. Children (3 to 5 years old), U.S. adults, and adults from a Bolivian indigenous group spontaneously induced recursive structures from ambiguous training data. In contrast, monkeys did so only with additional exposure. We quantify these patterns using a Bayesian mixture model over logically possible strategies. Our results show that recursive hierarchical strategies are robust in human thought, both early in development and across cultures, but the capacity itself is not unique to humans.