Learning of spatial configurations of a co-actor's attended objects in joint visual search.

Regarding the effects of joint action on visual memory, previous research has focused on the memory of a single object that a participant and their co-actor attended together (i.e., a shared situation), while the literature on memory has demonstrated that spatial regularity composed of multiple objects can also be learned. We aimed to examine whether the visuospatial regularity of the co-actor's attended objects could be strongly encoded. We repeatedly presented the same configuration of two targets and two sets of distractors in different colors (i.e., blue and red) to participants. In Experiment 1, pairs of participants simultaneously searched for the same target in the joint group while individual participants searched for the target alone in the single group. As a result, greater facilitation in reaction time was observed in earlier epochs in the joint group, reinforced by the learning of visuospatial regularity, compared to the single group. Experiment 2 examined whether the co-actor's attended context could be strongly encoded although two persons simultaneously searched for different targets (i.e., parallel situation) such that one searched for the blue target and the other for the red target. The results showed no evidence regarding participants' learning visuospatial regularity of the co-actor's attended objects, indicating that co-actor's learning information cannot be shared in this situation. This study revealed that facilitation of visuospatial learning in joint action would require two individuals to attend to the same objects when they perform the task.