Publications

Crowding occurs when nearby flankers hinder the identification of a target object. Crowding is feature integration over an inappropriately large region, but what determines the size of that region? According to bottom-up proposals the size is that of an anatomically determined isolation field. According to top-down proposals the size is that of the spotlight of attention. Here we investigate the role of attention in crowding using the change blindness paradigm. We measure capacity for widely and narrowly spaced letters during a change detection task, with or without an inter-stimulus cue. Consistent with both bottom-up and top-down accounts, we find that standard crowding manipulations – reducing spacing and adding flankers – impair uncued change detection performance. However, the same crowding manipulations fail to impair cued change detection. The cue relieves crowding. This has been sought but never found before. We suppose that object recognition consists of several steps: detection, segmentation, and integration. Perhaps feature detection is always followed by a coarse, pre-attentive segmentation, which is sometimes followed by a further, finer segmentation (triggered by an inter-stimulus cue), before the final integration of all the features within each segment.