Submitted on December 19, 2006
Accepted on February 2, 2007
Multiple saccades are more automatic than single saccades
Paul van Donkelaar1*, Sandy Saavedra1, and Marjorie Woollocott1
1 Human Physiology, University of Oregon, Eugene, Oregon, United States
* To whom correspondence should be addressed. E-mail: paulvd{at}uoregon.edu.
In this paper we demonstrate that when a peripheral object is foveated by a sequence of multiple saccades, the initial saccade in the sequence is initiated markedly faster than a single accurate saccade to the same object. We suggest that multiple saccades represent a more automatic form of oculomotor planning that may be the result of a reduced influence from the cerebral cortex. To test this we compared single and multiple saccade characteristics across development. We find that in contrast to the reduction in the latency of single saccades that is observed across development, the latency of initial saccades in multiple saccade sequences is remarkably stable across all age groups. Moreover, the longer the latency of this initial saccade, the more accurate it is, suggesting that there is a relation between the degree of procrastination and the accuracy of the response. Finally, the frequency with which multiple saccades occurred within each age group was positively correlated with the tendency to generate erroneous saccades during a fixation control task. Taken together, the present data suggest that multiple saccades are generated in a more automatic manner than single saccades.
