Cueing and pop-out

We describe experiments on the dynamics of pop-out from orientation. Target lines at an oblique orientation and orthogonal background elements were presented with various onset delays, and subjects' performance in target detection was measured. Detection rates increased for short delays compared to synchronous stimulus presentation, with a maximum at delta t = 30-60 ms. Control experiments showed that this effect did not reveal specific interactions between target and background lines; a similar effect was obtained when targets were cued with non-oriented stimuli presented shortly before stimulus onset. Specific and non-specific cues improved the target detection rate even when four cues, at different potential target positions were shown simultaneously. Non-localized cues, however, and cues at positions irrelevant for the task did not improve performance. While the effect might partially resemble the temporal modulation transfer function of the visual system, we did not find evidence for other dynamic processes in the tested time intervals (10-300 ms), in particular not for synchronization effects as assumed to provide perceptual linking of background elements.