Detecting When the Mind Wanders Off Task in Real-time: An Overview and Systematic Review

Research on the ubiquity and consequences of task-unrelated thought (TUT; often used to operationalize mind wandering) in several domains recently sparked a surge in efforts to create "stealth measurements"of TUT using machine learning. Although these attempts have been successful, they have used widely varied algorithms, modalities, and performance metrics - making them difficult to compare and inform future work on best practices. We aim to synthesize these findings through a systematic review of 42 studies identified following PRISMA guidelines to answer two research questions: 1) are there any modalities that are better indicators of TUT than the rest; and 2) do multimodal models provide better results than unimodal models? We found that models built on gaze typically outperform other modalities and that multimodal models do not present a clear edge over their unimodal counterparts. Our review highlights the typical steps involved in model creation and the choices available in each step to guide future research, while also discussing the limitations of the current "state of the art"- namely the barriers to generalizability.