Recognition memory fluctuates with the floodlight of attentional state

Attentional state fluctuates across time and influences what we remember. However, it is not yet understood whether fluctuations in attention affect memory for task-relevant and task-irrelevant information similarly. One possibility is that increased attentional state heightens the roving spotlight of selective attention, resulting in better filtering of irrelevant stimuli. Alternatively, better attentional state may act like a flickering floodlight, with increased attentional capacity allowing for greater processing of irrelevant stimuli. These hypotheses make opposite predictions for the subsequent memory of irrelevant stimuli. We collected two online samples (N1=188; N2=185) in which participants viewed a stream of trial-unique stimuli (500 trials) consisting of face images superimposed on scene images and were asked to perform a category judgment on either the faces (males vs. females) or scenes (indoors vs. outdoors) by pressing one key for frequent-category images (e.g., males, 90%) and a different key for infrequent images (e.g., females, 10%). Critically, the other category (scenes or faces) was completely irrelevant for the task. Following the sustained attention task, a surprise test probed recognition memory for both relevant and irrelevant stimuli using a 4-point scale. Logistic models tested whether sustained attention measures predicted memory accuracy. Attention lapses (errors to infrequent stimuli) were preceded by established RT signatures of sustained attention, speed (b1=.640, b2=.617) and variance (b1=-.296, b2=-.223; all ps<.001). As expected, memory was better for task-relevant items (b1=.722, b2=1.37; all ps<.001). Furthermore, correct performance on infrequent trials predicted memory for both task-relevant (b1=.134, p<.001; b2=.201, p<.001) and task-irrelevant (b1=.127, p<.001; b2=.111, p=.033) stimuli in both experiments. These results support the flickering floodlight view of attentional state, such that moments of high attention improve memory of relevant and irrelevant stimuli.