Human Eye Movement Behavior in Action Observation

In human joint action, visual attention is required to monitor the actions of others, but also for controlling and planning one's own actions. In a 'cup-clinking' scenario we investigated how people divide their attention between both tasks. Our participants first watched an actor and than performed their own task in the same way as the actor or in a pre-defined different (complementary) way. Using an eye-tracker, we found that people closely follow the action of the actor until they are given a signal to start their own movement. Interestingly, in the complementary condition our participants inspected the cup of the actor at the position they were going to grab their own cup. This result may merely reflect movement preparation. We go one step further and propose that visual information is extracted and transformed into parameters for the upcoming movement. Thus, attention may facilitate movement preparation while simultaneously the joint action partner is monitored.