Is attention necessary for perceiving gaze direction? It depends on how you look at it: evidence from the locus-of-the-slack method

Several researchers have studied how we process and perceive gaze direction. However, it is still unclear at which perceptual stage of gaze processing (encoding or/and categorization), attention is required to judge gaze direction. We report a study in which we manipulated the difficulty of gaze perceptual judgements (easy vs. difficult) and used the locus-of-slack method to test the role of different types of attention (spatial and central) in the encoding and categorization of gaze direction. In Experiment 1 we used the spatial cueing paradigm to investigate if gaze direction judgements can be carried out while spatial attention is diverted. In Experiment 2 we used the psychological refractory period (PRP) paradigm to determine whether judgement of gaze direction involves central attention processes. The findings demonstrate that gaze judgements require input attention (both for the encoding and categorization stage) but not central attention. The implications of the results are discussed.