Assessing individual differences in grouping strategy in visual working memory

Visual working memory is highly limited. Fortunately, we can use various strategies to improve performance. For example, we can make use of grouping cues, such as an illusory shape (Kanizsa figure), to optimize encoding and storage of information. However, it remains unclear how strategy use varies across individuals. In the current study, we examined whether working memory ability is related to individual differences in the use of grouping strategy. We manipulated whether the items formed Kanizsa figures or were randomly oriented in an orientation change detection task. We explicitly informed participants of the manipulation. Moreover, we independently assessed visual working memory capacity in a colour change detection task. In Experiment 1, there was better memory performance for Kanizsa figures versus randomly oriented items. Importantly, we found that individuals with higher working memory capacity showed a larger Kanizsa benefit. In Experiment 2, we still found a memory benefit for Kanizsa figures when we sequentially presented the inducers. This suggests that participants are able to use more abstract rules to strategically encode items. Furthermore, we again found that high working memory capacity corresponds to a larger Kanizsa benefit, although this finding was less robust across multiple analysis methods. Taken together, these findings show that individual differences in working memory ability predict effective use of grouping strategy. Moreover, these individual differences may partly reflect grouping based on high-level knowledge.