Evidence for social awareness comes in part from perspective taking. If you can share the direction of gaze of another person, and you know that the other person is gathering information by looking in that direction (other awareness), then you can understand what they are looking at, and how that might benefit you. Many scientists have argued that visual co-orienting and following gestures such as pointing are essential abilities to learn the human language, and very young infants show an ability to do both. We wanted to see to what extent tamarins followed these cues and used them to find treats that were hiddent.
Here Mark Lickteig (2001) first hides a treat under one of two cups when both cups are trapped under a box barrier. This prevented the monkeys from seeing where the treat actually was hidden. Next Mark would use a variety of cues on different trials, including head and eye gaze only, eye gaze (or glance) only, head/eye gaze and pointing, head/eye gaze and touching/pointing, for example, to see if the monkeys would use these cues to find the treat. Our evidence shows that tamarins quickly and naturally follow most of these social cues, except for the glance cue which involves the gaze direction without the head oriented in the same way. Tamarins' eyes do not move more much in their flat faces and it seems more easy for them to assume head orientation rather than the direction of the eye/pupil itself is the useful social cue coming from the observing other.
Read the article published on visual co-orientation (2002).
CITATION: Neiworth, J. J., Burman, M. A., Basile, B. M., & Lickteig, M. T. (2002). Use of experimenter-given cues in visual co-orienting and in an object-choice task by a new world monkey species, cotton top tamarins (Saguinus oedipus). Journal of comparative psychology (Washington, D.C. : 1983), 116(1), 3–11. https://doi.org/10.1037/0735-7036.116.1.3