Mind-wandering: when is it helpful, when does it harm?

Mind-wandering--task-unrelated thinking--occurs roughly 50% of the time. This means it occurs frequently while participants are doing the cognitive tasks we study in the laboratory. I will discuss our recent work on detecting mind-wandering with EEG classifiers. in addition, I will show how computational theories of mind-wandering can explain when it benefits task performance, and when it is not so useful. Together, these model-driven and data-driven approaches help us to understand how, when and why we mind-wander.