Prism adaptation while tracking and saccading

It is known that positional discordance between the spatial senses is a sufficient condition for prism adaptation of registered eye-in-head position. In this experiment adaptation was carried out under conditions in which Ss viewed their feet while making extensive tracking or saccading movements of their eyes. It has been claimed that tracking makes available less precise position information than saccading (Festinger and Canon 1965), but it is found that both modes are equally successful in causing this form of adaptation. It is concluded that either tracking and saccading yield equally valid estimates of eye-in-head position, or that the normal straight ahead position of the eye is a unique reference position.