Attentional oblique effect when judging simultaneity.

We extended the investigation of the oblique effect in two novel ways: from stimulus-driven vision to visual attention and from space to time. Participants fixated the center of briefly flashed displays that contained a temporally varying Gabor stimulus in each of the four peripheral quadrants. Across trial blocks, we manipulated which two of the four peripheral stimuli were to be selected for a simultaneity judgment. Simultaneity judgments were significantly worse for obliquely (diagonally) attended targets than for cardinally (horizontally or vertically) attended targets, despite identical retinal stimulation across all attentional conditions. The impairment in judging the simultaneity of obliquely attended targets occurred between and within lateral hemifields, despite significantly greater temporal acuity for the left hemifield. The oblique effect in simultaneity judgments disappeared when the same targets were presented without temporally varying stimuli at distractor locations-a finding that implicates selective attention. Intriguingly, the oblique effect in excluding stimuli at distractor locations also disappeared when participants viewed the original displays but attended to spatial frequency rather than to simultaneity. These findings raise the possibility of different spatial integration windows when attending to spatial versus temporal features, even when those features are co-presented in space and time.