conducted on mind-wandering. John Antrobus and Jerome L. Singer developed a questionnaire and discussed the experience of mind-wandering. This questionnaire, known as the Imaginal Processes Inventory (IPI), provides a trait measure of mind-wandering and it assesses the experience on three dimensions: how vivid the person's thoughts are, how many of those thoughts are guilt- or fear-based, and how deep into the thought a person goes. As technology continues to develop, psychologists are starting to use functional magnetic resonance imaging to observe mind-wandering in the brain and reduce psychologists' reliance on verbal reports. Research methods Jonathan Smallwood and colleagues popularized the study of mind-wandering using thought sampling and questionnaires. Mind-wandering is studied using experience sampling either online or retrospectively. One common paradigm within which to study mind-wandering is the SART (sustained attention to response task). In a SART task there are two categories of words. One of the categories are the target words. In each block of the task a word appears for about 300 ms, there will be a pause and then another word. When a target word appears the participant hits a designated key. About 60% of the time after a target word a thought probe will appear to gauge whether thoughts were on task. If participants were not engaged in the task they were experiencing task-unrelated thoughts (TUTs), signifying mind-wandering. Another task to judge TUTs is the experience sampling method (ESM). Participants carry around a personal digital assistant (PDA) that signals several times a day. At the signal a questionnaire is provided. The questionnaire questions vary but can include: (a) whether or not their minds had wandered at the time of the (b) what state of control they had over their thoughts and (c) about the content of their thoughts. Questions about context are also asked to measure the level of attention necessary for the task. One process used was to give participants something to focus on and then at different times ask them what they were thinking about. Those who were not thinking about what was given to them were considered "wandering". Another process was to have participants keep a diary of their mind-wandering. Participants are asked to write a brief description of their mind-wandering and the time in which it happened. These methodologies are improvements on past methods that were inconclusive. Neuroscience Mind-wandering is important in understanding how the brain produces what William James called the