Everyday experience suggests a close relationship between pursuit eye movements and direction of attention. As yet, the role of attention in SPEM performance has been discussed mainly in the literature on disturbed SPEM's in schizophrenia. The assumption that SPEM's benefit from the allocation of attentional resources was tested by comparing SPEM performance in single and dual task conditions.

Eye movements were electro-oculographically recorded in 27 healthy subjects who tracked a visual target which moved horizontally with constant or unpredictably changing velocity. In some trials, subjects performed additional auditory discrimination tasks varying in difficulty.

The auditory distracter tasks suited to focus attentional capacity to processing modalities other than those used for the concurrent eye tracking task not only left SPEM performance unaffected but even led to an improvement of tracking accuracy. When difficulty of the secondary task was increased, SPEM performance was insensitive to this manipulation if the target movement was highly predictable.

The independence of tracking error from secondary task difficulty in the constant velocity tracking condition suggests that eye tracking can be done in the automatic mode, at least under the conditions used here. Even more, it seems that controlled processing of the eye movement is dysfunctional as it interferes with the skilled automatic mode that permits optimal tracking. In the laboratory situation, single task tracking induces the allocation of resources to the oculomotor process rather than to target analysis due to the fact that the target usually has no task significance other than being the eye tracking target. If visual or auditory analysis tasks are added to the pure eye tracking task, the natural situation is restored as attention is redirected to the object analysis process.