Abstract
When performing everyday tasks our eyes are usually directed at the object or objects that are relevant for what we are doing at that moment. Sometimes it is advantageous to plan ahead, in which case our eyes can move on before the current action has finished. Moreover the eyes are not necessarily directed towards the object with which we intend to interact, but can also be directed to a position at which we expect information that is critical for successfully performing the task to become available, such as the position at which a ball that one intends to catch or hit will bounce. Thus eye movements may indicate the information that is critical for guiding an action. We measured eye movements (and movements of the head and hand) during an interception task in which subjects had to hit moving virtual targets towards a goal. The eyes were usually pursuing the target as the hand moved towards it. Gaze was seldom directed at the hand. Subjects sometimes glanced at the goal before starting to move their hand. They started systematically shifting their gaze from the target to the goal, presumably in order to see whether their hit was successful, from about 80ms before the hand hit the target, which is about when visual information is no longer useful for guiding the hand to the best position on the target. The position at which the hand intercepted the target hardly varied across trials, so the fact that subjects pursued the target with their eyes, rather than looking at the interception point and waiting for the target to arrive, suggests that we are better at judging where a moving target will be at a given time when we pursue it.