Abstract
Collections of visual objects can be grouped and statistical properties of the group encoded as ensemble features. It is known that ensemble features can be represented from a group of multiple items from a very brief display. In the current study, we measured the time-course of consolidation of average orientation into visual working memory and compared it to that of individual orientation. There were two separate blocks for individual orientation and ensemble orientation. For both blocks, participants performed a change-detection task for orientations of colored gratings, and shortly after the presentation of the memory array, pattern masks were presented to disrupt further consolidation (a method similar to Vogel et al, 2006). The stimulus onset asynchrony (SOA) was varied randomly from trial to trial. Half of the trials in a block included a change: either the orientation of one of the individual gratings (individual block) or the average orientation of one set of gratings (ensemble block). Participants indicated whether the two arrays were the same or different. The pattern of performance as a function of SOA for the individual block was consistent with a previous study reporting the consolidation of color for individual items (Vogel et al., 2006). Important and new, the pattern of performance as a function of SOA was identical across the individual and ensemble blocks. The rate of consolidation for the ensemble feature was comparable to that for the individual feature. This result suggests that ensemble features are extracted from an ensemble group just as an individual feature is extracted from a single object with the same rate of consolidation time required.