Abstract
Temporal crowding, classical masking and spatial crowding are 3 phenomena with which target identification is impaired by the presence of other irrelevant stimuli (distractors). With temporal crowding and masking the distractors appear before and/or after the target at the same location, but with masking, the inter-items SOAs are considerably shorter. With spatial crowding, the distractors surround the target in space rather than in time. Here, we examined whether the processes mediating these 3 phenomena are similar or different. We used a continuous orientation report task in a temporal crowding paradigm. Critically, a similar continuous report task was previously employed with both classical masking and spatial crowding, allowing us to compare these previous outcomes with those observed in this study. Our observers viewed a sequence of 3 randomly oriented items separated by varying SOAs (170–475 ms), and had to reproduce the target’s (middle item) orientation. On some trials (baseline trials) only the target appeared. The target and distractors were either similar (Experiments 1 & 2) or dissimilar (Experiment 3). Orientation error distributions were analysed with a mixture model analysis. In all 3 experiments, SOA (target-distractor distance in time) and distractors presence affected the standard deviation of the Gaussian distribution and substitution rate, but not guessing rate. This pattern of results is very different from that found for classical masking or spatial crowding. With masking, SOA mainly affected guessing rate, and with spatial crowding target-distractor spacing mainly affected guessing and substitution rate. Such different results suggest that these 3 phenomena involve different processes: reduction of signal-to-noise ratio mediates masking and spatial crowding, while impairment of encoding precision occurs only with temporal crowding. Still, the 2 types of crowding share some commonalities because with both, manipulating target-distractor distance (in time or space) and target-distractor similarity affected substitution rate.