Modification of smooth pursuit initiation by target contrast

It has been demonstrated that in gap pursuit tasks, smooth pursuit latency is reduced. This ‘gap effect’ is modified by factors such as gap duration and task context. We have now investigated whether it is also modified by an important visual parameter—the contrast of the pursuit and fixation targets. We found that while pursuit target contrast is an important determinant of pursuit latency, fixation target contrast had very little effect on pursuit latency. Neither pursuit nor fixation target contrast altered the gap effect on pursuit latency. Our results suggest that while visual parameters, like contrast, may modify the visual processing underlying pursuit initiation, the processing underlying the gap effect is separate and distinct.