Interaction-Mediated Tool Use Differently Enhances Physical and Social Cognition in Macaques (Macaca fascicularis)

In primates, learning to use a tool modulates cognitive functions related to the physical properties of objects. However, the impact of tool-use learning on social aspects of cognition has not been explored. We addressed this question via a training paradigm by using six, adult, long-tailed macaques (Macaca fascicularis), who were born in captivity and housed in the animal facility of the Department of Neuroscience and Rehabilitation of the University of Ferrara, Italy. We tested the effects of interaction-mediated tool use on overall cognitive performance in an experimental group (n = 2 males and n = 1 females). To evaluate changes in cognitive performance, we applied the Primate Cognition Test Battery at different stages of the training procedure that involved an interaction between the animal and an experimenter and the macaque using a rake to retrieve food items. As a control, we evaluated the performance of an age- and sex-matched group performing an interactive, manual grasping task. Several parameters related to the recognition of the position and noise of specific objects (i.e., space and causality in physical cognition), and those related to image-object association and object pointing to draw the attention of experimenter (i.e., communication aspects of social cognition) showed a significant improvement in the interaction-mediated tool-use group after the training period. The effects were transient, but the enhancement related to the noise and object pointing persisted for 35 days without further training. The control group showed no changes in cognitive performance. Our results show that interaction-mediated tool use enhances cognitive performance in both physical and social cognition domains.