Localization during Pursuit Eye Movement

Abstract

Humans are very good at acquiring complex skills. More than probably any other species they learn a large array of new capabilities after they are born. Special institutions (e.g. schools, sporting clubs, handwork courses, etc.) have been put into operation to optimize the learning of such skills. It can be very pleasurable to acquire or optimize your skills, as is evident from the popularity of sporting clubs. In sports, precise coordination of different body parts is generally important. You must be somewhere at exactly the right time, for example to catch a ball when playing baseball. In other cases you must bring an object like a ball or a dart in such a condition that after you lose contact with it (and thus control over it) the object will move to some intended position. The timing and positioning requirements in sports can be very demanding (e.g. Regan 1992), but ordinary actions in daily life also require precise co-ordination. For example, when grasping an object that has a width of 10 centimeters while you are walking at a moderate speed (i.e. 5 km/hour), your hand will move past the object in less than one tenth of a second. In order to be successful you not only have to position your hand at the right place but it also has to be there at the right time, which is often a very short period. Knowing "the right place" is also far from easy, because at the moment that the brain sends the movement commands to the muscles, the object of interest is not there yet. So, obviously, some kind of prediction must be made. Eye movements are very important to gather the required information for such a prediction. For example, Land and Fumeaux (1997) argue that the eyes move in ways that optimize the uptake of information that is useful in such diverse activities as playing table tennis, reading music and driving a car. Moreover, knowing where and knowing when are not independent. Planning to contact a moving object later also means that it must be contacted at another position. For example, when walking past a stationary object you could plan to grasp the object when it is to the right and in front of your body, which would require the arm to move obliquely forwards. Alternatively, you could plan to grasp the object when it is purely to the right of your body, which would require the arm to move rightwards. When you are walking past the object you should start your movement earlier in the first than in the second case.