https://phaidra.vetmeduni.ac.at/o:2963 The Joint Simon task is not joint for capuchin monkeys Martínez, Mayte Mayte Martínez 0000-0002-8380-3073 University of Veterinary Medicine Vienna / Georgia State University Brosnan, Sarah F. Sarah F. Brosnan Georgia State University Babb, Matthew H. Matthew H. Babb Georgia State University Range, Friederike Friederike Range 0000-0003-3127-5536 University of Veterinary Medicine Vienna Nature Portfolio text eng Human cooperation can be facilitated by the ability to create a mental representation of one's own actions, as well as the actions of a partner, known as action co-representation. Even though other species also cooperate extensively, it is still unclear whether they have similar capacities. The Joint Simon task is a two-player task developed to investigate this action co-representation. We tested brown capuchin monkeys (Sapajus [Cebus] apella), a highly cooperative species, on a computerized Joint Simon task and found that, in line with previous research, the capuchins' performance was compatible with co-representation. However, a deeper exploration of the monkeys' responses showed that they, and potentially monkeys in previous studies, did not understand the control conditions, which precludes the interpretation of the results as a social phenomenon. Indeed, further testing to investigate alternative explanations demonstrated that our results were due to low-level cues, rather than action co-representation. This suggests that the Joint Simon task, at least in its current form, cannot determine whether non-human species co-represent their partner's role in joint tasks. Animals; Cebusphysiology; Cues http://creativecommons.org/licenses/by/4.0/ https://phaidra.vetmeduni.ac.at/api/object/o:2963/download 10.1038/s41598-024-55885-x https://phaidra.vetmeduni.ac.at/o:605 application/pdf Scientific Reports 14(1) (2024) Scientific Reports 14 1 1.70 MB 2024