Abstract
We can perceive ensemble information such as average size and orientation quickly and efficiently. Such efficient statistical perception is observed both with simultaneous and sequential presentation of objects. Mean size information of simultaneously presented objects influences visual working memory (VWM) for each object. However, few studies have addressed the relationship between VWM for ensemble and for single items with sequentially presented objects. This study investigated characteristics of VWM for ensemble formed from sequentially presented items, compared with VWM for ensemble from simultaneously presented items. Participants viewed a sequence of randomly oriented arrow stimuli with 100ms duration for each item and 1000ms inter-item interval, and reported the orientation of their mean or of a particular item. In Experiment 1, participants reported the mean orientation of 4- or 12-item sequence, and multiple regression analysis showed that the beta weight of each item increased as the serial order, indicating a recency effect. To test whether the recency effect simply reflects the property of sequential memory task, Experiment 2 asked participants to report the orientation of all 4 items, and the recency effect disappeared, suggesting that the recency effect is specific to the computation of mean orientation. Next, to examine whether the recency effect occurs only when memory for single items is unnecessary, Experiment 3 asked participants to report either a single item or the mean, depending on the response cue presented after the sequence, and mean orientation trials still showed the recency effect. Furthermore, VWM precisions for a single item and for the mean were comparable, which is inconsistent with studies using simultaneous presentation reporting higher precision with the mean. Taken together, formation and maintenance of mean with sequentially presented items in VWM is distinct from those with simultaneously presented items, and shows a recency effect specific to the mean computation.
Meeting abstract presented at VSS 2017