Macaque species with varying social tolerance show no differences in understanding what other agents perceive

Sensitivity to line-of-sight in tolerant versus despotic macaques (Macaca sylvanus and Macaca mulatta)

Complex social life is considered important to the evolution of cognition in primates. One key aspect of primate social interactions concerns the degree of competition that individuals face in their social group. To examine how social tolerance versus competition shapes social cognition, we experimentally assessed capacities for flexible gaze-following in more tolerant Barbary macaques (Macaca sylvanus) and compared to previous data from despotic rhesus macaques (Macaca mulatta). Monkeys experienced one of two possible conditions. In the barrier condition, they observed an actor look upwards into an overheard barrier, so they could not directly see the target of the actor's gaze without reorienting. In the no barrier condition, they observed an actor look upwards without a barrier blocking her line-of-sight, so they could observe the target of the actor's gaze by also looking upwards. Both species (N = 58 Barbary macaques, 64 rhesus macaques) could flexibly modulate their gaze responses to account for the demonstrator's line of sight, looking up more often when no barrier was present, and this flexible modulation declined with age in both species. However, neither species preferentially approached to look inside the barrier when their view of the target location was obscured, although rhesus macaques approached more overall. This pattern suggests that both tolerant and despotic macaques exhibit similar capacities to track other's line of sight and do not preferentially reorient their bodies to observe what an actor looks at in this situation. This contrasts with other work indicating that competitive primates are especially adept at some aspects of theory of mind. Thus, it is important to understand both the similarities and differences in the social-cognitive abilities of primates with different social styles. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

How do non-human primates represent others' awareness of where objects are hidden?

Although non-human primates (NHPs) generally appear to predict how knowledgeable agents use knowledge to guide their behavior, the cognitive mechanisms that enable this remain poorly understood. We assessed the conditions under which NHPs' representations of an agent's awareness break down. Free-ranging rhesus macaques (Macaca mulatta) watched as an agent observed a target object being hidden in one of two boxes. While the agent could no longer see the boxes, the box containing the object flipped open and the object either changed in size/shape (Experiment 1) or color (Experiment 2). Monkeys looked longer when the agent searched for the object incorrectly rather than correctly following the color change (a non-geometric manipulation), but not the size/shape change (a geometric manipulation). Even though the agent maintained knowledge of the object's location in both cases, monkeys no longer expected the agent to search correctly after it had been geometrically (but not non-geometrically) manipulated. Experiment 3 confirmed that monkeys were sensitive to the color manipulation used in Experiment 2, making it unlikely that a failure to perceive the color manipulation accounted for our findings. Our results show that NHPs do not always expect that knowledgeable agents will act on their knowledge to obtain their goals, consistent with heuristic-based accounts of how NHPs represent others' mental states. These findings also suggest that geometric changes that occur outside the agent's perceptual access may disrupt attribution of awareness more so than non-geometric changes.