Abstract
We investigated the allocation of visuo-spatial attention during dynamic viewing with a dual task. The primary search task (K, H, O, or V among Xs) required sequential left-to-right eye movements. An additional manual detection response was made to a visual probe that appeared early or late after the onset of one critical eye fixation (25 or 170 ms probe delay). The probe appeared either to the left, or directly above, or to the right of the currently fixated character (−10, −5, 0, +5, or +10 characters probe eccentricity).
As predicted from research with single-eye movement tasks, probe detection became faster near the location of the forthcoming eye fixation, indicating an attention shift to that location. Fixation times increased as a consequence of probing, but less so when the probe appeared in the right compared to the left hemifield. Saccade lengths decreased as a result of probing, but remained largest when the probe appeared at +10 characters. These data support the notion of goal-directed attention shifts prior to eye movements in natural viewing.
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