Categorically Distinct Subsets Allow Flexible Memory Selection in Hybrid Search.

In many everyday situations, we search our visual surroundings for any one of many memorized items held in memory, a process termed hybrid search. In some cases, only a portion of the memorized mental list is relevant within a specific visual context, thus, restricting memory search to the relevant subset would be desirable. Previous research had shown that participants largely fail to "partition" memory into several distinct subsets, on a trial-by-trial basis. However, given the known role of semantic content in long-term memory organization, we hypothesized that semantically defined subset categories might serve as a more powerful means for flexible memory selection in dynamic hybrid search situations. Experiment 1 revealed that, indeed, semantic characteristics (i.e., object category), but not perceptual features (e.g., arbitrary color), can provide a firm basis for flexible memory partitioning. Experiments 2 and 3 further showed that such memory partitioning is costless and is independent of the nature of the surrounding visual distractors (i.e., a categorically homogeneous or heterogeneous display). These findings demonstrate that confining one's memory search to a currently relevant subset of items is highly effective when the different memory subsets are defined by clear semantic categories. The results underscore the importance of conceptual information in the organization of activated long-term memory and in forming the basis for a flexible trial-by-trial memory selection. Our findings further highlight the relationship between visual search and memory search, and they may shed light on the processes contributing to a successful construction of bounded episodes in long-term memory. [ABSTRACT FROM AUTHOR]