Three experiments investigated the relationship between subjective experience and attentional lapses during sustained attention. These experiments employed two measures of subjective experience to examine how differences in awareness correspond to variations in both task performance and psycho-physiological measures . This series of experiments examine these phenomena during the Sustained Attention to Response Task . The results suggest we can dissociate between two components of subjective experience during sustained attention: task unrelated thought which corresponds to an absent minded disengagement from the (...) task and a pre-occupation with one's task performance that seems to be best conceptualised as a strategic attempt to deploy attentional resources in response to a perception of environmental demands which exceed ones ability to perform the task. The implications of these findings for our understanding of how awareness is maintained on task relevant material during periods of sustained attention are discussed. (shrink)