Fluctuations in sustained attention explain moment-to-moment shifts in children's memory formation

Children get a lot of attention for being powerful “learning machines” in the popular press, but the truth is they remember much less than adults. Even still, many of children’s individual memories are rich and complex and similar in quality to adults’, suggesting what improves in development is not just the quality of our memories, but the frequency with which we form them. Here, we ask why children form memories less often than adults; instead of focusing on memory mechanisms, we focus on an entirely separate aspect of cognition: sustained attention. In adults, sustained attention fluctuates to shape memory in each moment, but we know little about how attention fluctuates in childhood to shape memory formation. To address this gap, 7–10-year-old children and adults (n=120) completed a sustained attention task in which they classified trial-unique images as living or nonliving. We then tested memory for each image, and related attentional fluctuations during classification to subsequent memory. We found that attention fluctuated between states more frequently in children than adults, and that across children, attentional lapse rates correlated with lower memory performance. Within participants, attentional fluctuations shaped the fate of individual memories, such that lapses predicted memory failures. While these fluctuations shaped memory for expected events in both children and adults, they only shaped memory for unexpected events in children, highlighting their particularly detrimental and pervasive influence in development. Our findings raise the possibility that broad developmental differences in cognitive performance reflect the ability to sustain attention.