Abstract
Last year we reported an attentional oblique effect in simultaneity judgments (Kelly & Matthews, 2010 VSS abstract). Gabor stimuli were presented in four corners of the screen (14.55 deg diagonally from fixation) and changed orientation synchronously or asynchronously. Two were pre-cued as targets on each trial. Participants judged whether or not the change in orientation happened simultaneously for the cued targets. Performance (d′) was significantly worse for target pairs that were diagonally rather than horizontally or vertically aligned. Here we present new data and error analyses (false alarms vs. misses) demonstrating that this oblique effect when attending to simultaneity reflects erroneously integrated information from irrelevant spatial locations. That is, the oblique effect arose from false alarms, not misses. This excessive spatial integration for obliquely attended targets occurred between and within lateral hemifields, despite significantly greater temporal acuity (demonstrated by a significantly lower miss rate) in the left hemifield. Within-hemifield data were obtained by moving the fixation point from the center of the screen to either side, such that the stimuli on the screen fell entirely within either the left or the right hemifield. A perceptual learning experiment demonstrated that the effect was task specific: significant learning on the simultaneity task did not generalize to a task with identical displays wherein participants judged spatial frequency differences rather than simultaneity. This suggests different spatial integration windows for different attended features (simultaneity versus spatial frequency), even when those features are co-presented in space and time.