Abstract
An exemplar property of goal-directed saccades is the undershooting of veridical target location: a property that has been tied to an energy minimizing bias that reduces the physiological and psychological costs of target overshooting. Interestingly, however, Kapoula (1985) reported that task properties and the range of target eccentricities presented within discrete trial blocks engenders a saccade overshooting bias (so-called range effect). In the present investigation, we sought to determine whether the range of target eccentricities associated with serially presented blocks modulates saccade endpoint bias. To that end, participants (N=20) completed saccades to briefly (i.e., 50 ms) presented targets in two separate blocks. The first block employed a "small" range of target eccentricities (i.e., 3, 5.5, 8, 10.5, and 13[sup]o[/sup]), whereas the second block entailed a "large" range of eccentricities (i.e., 10.5, 13, 15.5, 18, and 20.5[sup]o[/sup]). Notably, the ordering of blocks was constant and two common eccentricities were associated with each (i.e., 10.5 and 13[sup]o[/sup]). Thus, if a range effect influences goal-directed saccades then the undershooting bias associated with the 10.5[sup]o[/sup] and 13[sup]o[/sup] targets in the first block should exhibit an overshooting bias in the second block. Results for saccade amplitude revealed a reliable undershooting of all target eccentricities in both blocks. Moreover, a between-block comparison of the congruent target eccentricities (i.e., 10.5[sup]o[/sup] and 13[sup]o[/sup]) yielded an equivalent undershooting bias. Therefore, results provide no evidence to support a range effect in oculomotor control. Instead, the results are consistent with models of energy minimization and the assertion that oculomotor responses are designed to minimize movement time and energy expenditure. This study was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC).
Meeting abstract presented at VSS 2013