Development of a monkey avatar to study social perception in macaques

Following the expanding use and applications of virtual reality in every-day life, dynamic virtual stimuli are of increasing interest in cognitive studies. They allow for control of features such as gaze, expression and movement, which may help to overcome limitations of using either static or poorly controlled real stimuli. In using virtual stimuli however, one must be careful to avoid the uncanny valley effect - where realistic stimuli can be perceived as eerie, and induce an aversion response. At the same time, it is important to establish whether responses to virtual stimuli mirror responses to depictions of a real conspecific. In the current study, we describe the development of a new avatar with realistic features for nonhuman primates, the primatar. As a first step towards validation, we assessed how monkeys respond to images of this avatar compared to images of real monkeys, and an unrealistic avatar. We also compared responses between original images and scrambled as well as obfuscated versions of these images. We measured looking time to images in six free moving long-tailed macaques (Macaca fascicularis) and eye movement exploration behaviour in three rhesus macaques (Macaca mulatta). Both groups showed more of such signs of overt attention to original images than scrambled or obfuscated images. In addition, we assessed whether the realistic avatar created an uncanny valley effect through decreased looking time, finding that in both groups, monkeys did not differentiate between real, realistic or unrealistic images. These results provide support for further development of our avatar for use in social cognition studies, and more generally for cognitive research with virtual stimuli in nonhuman primates. Future research needs to shed light on the source of the inconsistent findings for the uncanny valley effect in macaques, to elucidate the roots of this mechanism in humans.