Koops, K., Biro, D., Matsuzawa, T., McGrew W.C., & Carvalho, S. (2023). Appropriate knowledge of wild chimpanzee behavior (‘know-what’) and field experimental protocols (‘know-how’) are essential prerequisites for testing the origins and spread of technological behavior. Response to “Unmotivated subjects cannot provide interpretable data and tasks with sensitive learning periods require appropriately aged subjects” by C. Tennie and J. Call. Animal Behavior and Cognition, 10(2), 163-168.  https://doi.org/10.26451/abc.10.02.05.2023

We respond to the commentary by Tennie and Call (2023) on the article by Koops et al. (2022) in Nature Human Behaviour titled ‘Field experiments find no evidence that chimpanzee nut cracking can be independently innovated.’ Koops et al. (2022) showed that chimpanzee nut cracking is not a so-called ‘latent solution.’ Chimpanzees (Pan troglodytes verus) in the Nimba Mountains (Guinea) did not crack nuts when presented with nuts and stones in ecologically valid field experiments. In their Commentary, Tennie and Call (2023) argued that the experiments were inconclusive for two reasons: 1) the chimpanzees were not motivated to treat the nuts as food, and 2) the chimpanzees were not within the appropriate ‘sensitive learning period.’ In our response, we argue that Tennie and Call (2023) incorrectly use the term ‘motivation’ to mean ‘willingness to eat the nut’, which requires existing knowledge of the edibility of the nuts. We also point out that it is unnatural and uninformative to inject nuts with honey to motivate the chimpanzees to eat them, as suggested by Tennie and Call (2023). Finally, we highlight that Koops et al. (2022) tested appropriately aged subjects (N=32 immatures). Moreover, we argue that there is no evidence to suggest that there is a strictly sensitive learning period restricted to juvenility. Finally, we emphasize the need for researchers doing experiments in captivity to visit their study species in the wild, and for field researchers to be involved in efforts to design ecologically valid experiments in captivity.

Chimpanzee, Culture, Nut cracking, Sensitive learning period, Social learning