Investigating the reversed congruency effect of gaze through the lens of joint attention

Recent evidence has highlighted differences in attentional shifting elicited by gaze and arrow stimuli. Specifically, in a spatial Stroop task, arrows consistently produce a standard congruency effect (SCE; faster reaction times on congruent vs. incongruent trials). In contrast, averted gaze stimuli produce a reversed congruency effect (RCE; faster reaction times on incongruent vs. congruent trials). The origin of this discrepancy is still under debate. One hypothesis suggests that the RCE for gaze is driven by joint attention (the shared focus of two individuals on the same object). According to this view, during incongruent trials, gaze stimuli appear to look toward the fixation stimulus, thus creating an episode of joint attention with the participant. To investigate this possibility, we conducted four experiments where participants identified the direction of a peripheral target (gaze or arrow). We also varied the fixation stimulus (symbolic cross or real-world object) and added an oculomotor component, to enhance joint attention contexts. Results consistently showed an SCE for arrows and an RCE for gaze, regardless of fixation type and the request to perform an eye movement, suggesting that joint attention, as operationalised in the present study, may not fully explain the RCE elicited by gaze.