The color-word Stroop effect driven by working memory maintenance

Previous research has shown that holding a color word in working memory can produce interference effects in an intervening color-identification task, which mimics the classic color-word Stroop effect. Although this finding has previously been considered to suggest that the content of working memory can have behavioral consequences similar to those of externally perceived stimuli, it has remained unclear whether active internal maintenance of a color word indeed makes a critical contribution to the working memory Stroop effect. In the present study, we addressed this matter by asking participants to perform a color-identification task following display of either a congruent or an incongruent color word. By controlling for encoding strategy and/or maintenance demand across Experiments 1-4, we consistently showed that the magnitude of the congruency effect in color-identification performance was markedly larger when the recently presented color word was actively retained in working memory, as compared to when the color word was perceptually identified without working memory processing, when the color word had once been remembered but was no longer being actively maintained in working memory, or when the color word was retro-cued to be irrelevant to the working memory task. The findings therefore demonstrate a critical role for active internal maintenance of a color word in producing the working memory Stroop effect. In addition, Experiment 5 further showed that the working memory Stroop effect was sustained over time during the retention interval. Moreover, we found that the intervening color-identification task conversely influenced working memory maintenance, leading to poorer memory performance on incongruent than on congruent trials. We discuss the implications of these findings for understanding the linkage between working memory and attention.