Statistical processing of perceptual groups under working memory load

The visual system is capable of summarizing the average properties of sets of objects that exceed the limits of focused attention. While statistical processing is thought to involve distributing attention over the set as a whole, the possibility remains that it relies on the sampling of a few objects that remain within the limits of focused attention. In the present study we tested this question using a dual task paradigm. Participants performed a statistical processing task while maintaining items in working memory (colors in Experiment 1, spatial locations in Experiment 2). We hypothesized that even though working memory load would interfere with the encoding of individual items, it would not interfere with statistical processing accuracy. The difficulty of both the statistical processing and working memory tasks was varied: participants compared the average size of two sets of circles which differed by 5%, 10%, 15% or 20% in mean size, while maintaining two, four or zero items in working memory. In both experiments, participants performed less accurately in the statistical processing task as the difference in mean between sets decreased. Also, they showed expected memory accuracy decrements with increased memory load. However, as predicted, participants' performance in the statistical processing task was not influenced by working memory load. The results suggest that statistical properties are extracted from the set as a whole rather than from individually processed objects. Meeting abstract presented at VSS 2016