In a spatial Stroop task, the eye-gaze target produces the reversed congruency effect-responses become shorter when the gaze direction and its location are incongruent than when they are congruent. The present study examined the face inversion effect on the gaze spatial Stroop task to clarify whether the holistic face processing or part-based processing of the eyes is responsible for the reversed congruency effect. In Experiment 1, participants judged the gaze direction of the upright or inverted face with a neutral expression presented either in the left or right visual field. In Experiment 2, we examined whether face inversion interacted with facial expressions (i.e., angry, happy, neutral, and sad). Face inversion disrupted holistic face processing, slowing down the overall performance relative to the performance with upright faces. However, face inversion did not affect the reversed congruency effect. These results further support the parts-based processing account and suggest that while faces are processed holistically, the reversed congruency effect, relying on the extracted local features (i.e., eyes), may be processed in a part-based manner.

In the spatial Stroop task, an arrow target produces a spatial Stroop effect, whereas a gaze target elicits a reversed spatial Stroop effect. The reversed spatial Stroop effect has been explained by the unique attentional mechanisms of eye gaze. However, recent studies have shown that not only gaze but arrow targets produced a reversed spatial Stroop effect when embedded in a complex background. The present study investigated whether non-social targets produce a reversed spatial Stroop effect. We used the tongue, which generally does not convey social information, as a target in the spatial Stroop task, in addition to the conventional gaze and arrows. Participants judged the left/right direction of the target presented in the left or right visual field. While arrow and gaze targets replicated previous findings (spatial Stroop and reversed spatial Stroop effect, respectively), the tongue target produced a reversed spatial Stroop effect. These results are inconsistent with previous accounts emphasizing the unique status of eye gaze. We propose that temporal decay of the location code and response inhibition are responsible for the reversal of spatial interference.

Many studies have shown that the gaze of others produces a unique attentional process, such as the eye contact effect or joint attention. This study investigated the attentional process triggered by various types of gaze stimuli (i.e., human, cat, fish, and robot gaze). A total of 190 university students participated in three experiments. They performed a spatial Stroop task in which four types of gaze stimuli were presented as targets. Participants were asked to judge the direction of the target (left or right) irrespective of its location (left or right). The results showed that the human and the cat targets produced a reversed congruency effect (Experiments 1 and 2). In contrast to the human and the cat targets, the fish and the robot target did not produce the reversed congruency effect (Experiments 2, and 3). These results suggest that attention to the gaze of socially communicable beings (i.e., humans and cats) is responsible for the reversed congruency effect. Our findings support the notion that the theory of mind or social interaction plays an important role in producing specific attentional processes in response to gaze stimuli.

No abstract

In a spatial Stroop task, the eye-gaze target produces the reversed spatial Stroop effect—responses become shorter when the gaze direction and its location are incongruent than when they are congruent. The present study examined the face inversion effect on the gaze spatial Stroop task to clarify whether the holistic face processing or part-based processing of the eyes is responsible for the reversed spatial Stroop effect. In Experiment 1, participants judged the gaze direction of the upright or inverted face with a neutral expression presented either in the left or right visual field. In Experiment 2, we examined whether face inversion interacted with facial expressions (i.e., angry, happy, neutral, and sad). Face inversion disrupted holistic face processing, slowing down the overall performance relative to the performance with upright faces. However, face inversion did not affect the reversed spatial Stroop effect. These results further support the parts-based processing account and suggest that while faces are processed holistically, the reversed spatial Stroop effect, relying on the extracted local features (i.e., eyes), may be processed in a part-based manner.