Individual Variation in Encoding Strategy Optimization in Visual Working Memory: Evidence From a Change Detection Task

Extensive research has shown that differences in cognitive ability predict working memory (WM) performance. However, strategy use may also explain individual differences in WM. Here we explored individual variation in encoding strategy optimization in visual WM. Participants searched for a target that changed between two alternating displays that cycled until response. Critically, participants could freely choose between one red and one blue target, and the ratio of red to blue items varied randomly across trials. Therefore, the optimal strategy was to selectively encode items in the smaller colour subset. Results showed a general tendency to choose the optimal (small subset) target, but there were large individual differences in strategy choice, with many participants using sub-optimal strategies. While Experiment 1 found no relationship between ability and strategy, a larger-sample replication in Experiment 5 found a small, positive correlation between WM ability and strategy optimization. Experiment 2 showed that strategy use was not stable over time. Many participants spontaneously shifted to highly-optimal target choices, suggesting a sudden discovery of the optimal strategy. Experiment 3 confirmed the importance of explicit knowledge in strategy choice. Informing participants about the optimal strategy induced a large strategy improvement. Moreover, optimally-performing participants demonstrated explicit awareness of the optimal strategy. Experiment 4 showed that, even under greater task demands, when participants viewed the displays only once, strategy use was still sub-optimal. Our findings highlight strategy choice as an important source of individual variation, and therefore should be considered alongside ability to fully understand differences in WM.