Spontaneous eye blinks as temporal markers of internal attention

Eye blinks are among the largest physiological artefacts in electroencephalography and are typically removed from the recordings. Yet their timing may carry information about cognition. Here, we asked whether the temporal distribution of spontaneous blinks across trials provides a time-resolved behavioural signature of internal attentional focusing in working memory. In Experiment 1, blink-locked EEG analyses showed that blink timing was aligned with neural activity reflecting attentional focusing on a relevant internal representation. In Experiment 2, participants remembered the same visual information across conditions, but the relevant item was cued either early during storage, or later with presentation of the memory probe. Blink-frequency profiles shifted accordingly, increasing after the cue when selection was possible early and after the probe when selection was delayed. Post-cue blinks in the early-selection condition were also associated with better memory performance. Thus, more generally, spontaneous blinks might provide an unobtrusive chronometric signal for tracking latent cognitive processing.