Abstract

Two visual search experiments were conducted to investigate whether the line motion illusion results from the local facilitation of a line stimulus in the gradient of attention. In Experiment 1, color-defined search elements were presented as sudden-onset stimuli, and a line appeared between them. Subjects showed no difference between a target and distractors in inducing an illusory projecting sensation from a line following them. In Experiment 2, search element were presented through partial offset of premasks in order to prevent attentional capture by abrupt onset, and two stimulus onset asynchronies (SOAs) were applied to measure a temporal profile of the line motion illusion. The 150msec SOA condition produced the same result as Experiment 1, whereas the target induced more amount of illusion than the distractors with 250msec SOA. These results provide an evidence that spatial attention is not a necessary condition of the line motion illusion, suggesting that the line motion illusion may be a byproduct of binding process between a preceding stimulus and a subsequent line.