Do chimpanzees reason logically?

Jan M Engelmann; Lou M Haux; Christoph Völter; Hanna Schleihauf; Josep Call; Hannes Rakoczy; Esther Herrmann

doi:10.1111/cdev.13861

Do chimpanzees reason logically?

Child Dev. 2023 Sep-Oct;94(5):1102-1116. doi: 10.1111/cdev.13861. Epub 2022 Oct 18.

Authors

Jan M Engelmann¹, Lou M Haux², Christoph Völter³, Hanna Schleihauf^{1

4}, Josep Call⁵, Hannes Rakoczy⁶, Esther Herrmann⁷

Affiliations

¹ Department of Psychology, University of California, Berkeley, Berkeley, California, USA.
² Center for Adaptive Rationality, Max Planck Institute for Human Development, Berlin, Germany.
³ Messerli Research Institute, University of Veterinary Medicine Vienna, Medical University of Vienna, University of Vienna, Vienna, Austria.
⁴ Department for Primate Cognition, Georg-August-University Goettingen, Goettingen, Germany.
⁵ School of Psychology and Neuroscience, University of St. Andrews, St. Andrews, UK.
⁶ Department of Developmental Psychology, Georg-Elias Müller Institute of Psychology, Georg-August-University Goettingen, Goettingen, Germany.
⁷ Department of Psychology, University of Portsmouth, Portsmouth, UK.

PMID: 36259153
DOI: 10.1111/cdev.13861

Abstract

Psychologists disagree about the development of logical concepts such as or and not. While some theorists argue that infants reason logically, others maintain that logical inference is contingent on linguistic abilities and emerges around age 4. In this Registered Report, we conducted five experiments on logical reasoning in chimpanzees. Subjects (N = 16; 10 females; M = 24 years) participated in the same setup that has been administered to children: the two-, three-, and four-cup-task. Chimpanzees performed above chance in the two-cup-, but not in the three-cup-task. Furthermore, chimpanzees selected the logically correct option more often in the test than the control condition of the four-cup-task. We discuss possible interpretations of these findings and conclude that our results are most consistent with non-deductive accounts.