Concurrent prospective memory task increases mind wandering during online reading for difficult but not easy texts.

Many prior theories have tried to explain the relationship between attentional processes and mind wandering. The resource-demand matching view argues that a mismatch between task demands and resources led to more mind wandering. This study aims to test this view against competing models by inducing mind wandering through increasing the level of demands via adding a prospective memory task to cognitively demanding tasks like reading. We hypothesized that participants with a second task still in mind (unfinished group) engage more in task-unrelated thoughts (TUTs) and show less text comprehension compared to participants who think a second task is finished (finished group). Seventy-two participants had to study 24 items of a to-do list for a recall test. After a first cued recall of ten items, participants were either told that a second task was finished or that the recall was interrupted and continued later. All participants then started reading an easy or difficult version of the same unfamiliar hypertext, while being thought probed. Text comprehension measures followed. As expected, participants in the unfinished group showed significantly more TUTs than participants in the finished group when reading difficult texts, but, contrary to our assumptions, did not show better text comprehension measures when reading difficult text. Nevertheless, participants compensate for the influence of the second task by reading longer, which in turn has a positive effect on their reading knowledge. These findings support the resource-demand-matching model and thus strengthen assumptions about the processing of attention during reading.