Effects of location and form cuing on the allocation of attention in the visual field.

Two experiments were conducted which tested the effect of two different types of cues on the allocation of attention in the visual field. Subjects responded to a target appearing either 6.5 degrees to the right or to the left of fixation in a field filled with small randomly positioned line segments. The target form was either a circle or diamond in which a horizontal or vertical line segment was positioned. Subjects made a speeded discrimination response on the basis of the orientation of this line segment. In the first experiment, there was always one target at each trial. In the second experiment, both circle and diamond were presented left or right of fixation simultaneously whereby the line segment only appeared in one of the forms. In different conditions, the most likely target location (left or right) and form (circle or diamond) were cued. Control conditions served as a baseline for determining costs and benefits. Reaction time measures showed that the validity of the location cue resulted in both costs and benefits, whereas the validity of the form cue had no such effects. The results cannot be reconciled with the claim of zoom lens theories that spatial attention can switch between different modes of operations. They are also at odds with theories that claim that attention has no spatial locus. The results are consistent with a simple spotlight theory in which spatial attention involves selecting a particular restricted area of the visual field for which the perceptual efficiency is enhanced.