Efficiently judging where someone else is looking is important for social interactions, allowing us a window into their mental state by establishing joint attention. Previous work has shown that judging the gaze direction of a non-foveally-presented face is facilitated when the eyes of that face are directed towards the centre of the scene. This finding has been interpreted as an example of the human bias for misattributing observed ambiguous gaze signals as self-directed eye contact. To test this interpretation against an alternative hypothesis that the facilitation is instead driven by the establishment of joint attention, we conducted two experiments in which we varied the participants’ fixation location. In both
experiments we replicated the previous finding of facilitated gaze discrimination when the participants fixated centrally. However, this facilitation was abolished when participants fixated peripheral fixation crosses (Experiment 1) and reversed when participants fixated peripheral images of real-world objects (Experiment 2). Based on these data, we propose that the facilitation effect is consistent with the interpretation that gaze discrimination is facilitated when joint attention is established. This finding therefore extends previous work showing that engaging in joint attention facilitates a range of social cognitive processes.