Spontaneous Mind-Wandering Thought Content Is Less Constrained Than Controlled Internal Attention

Achieving a complete understanding of our internal thought processes requires us to understand the behavioral and neural distinctions underpinning controlled thoughts (internal attention) and spontaneous thoughts (mind-wandering). One unexplored question is whether thought content differs with differing levels of thought control. We had participants in an online study perform a mind-wandering task, report the content of their thoughts in their own words and categorize their thoughts based on content, where their thoughts were directed (externally or internally) and whether their thoughts were under their control. We computed sentence similarity of thought content through pre-trained sentence similarity models and found within-subject task-unrelated thought content was less similar than within other thought categories. We also found within-subject internally generated spontaneous thoughts were less similar than internally generated controlled thoughts, even when analyses were restricted to task-unrelated thoughts. Validation of sentence embeddings found thought content naturally clusters based on thought category. We finally found the number of task-unrelated internal spontaneous trials, but not controlled trials, correlated with mind-wandering survey measures. Overall, we find evidence for a meaningful distinction between controlled internal attention and spontaneous mind-wandering based on thought content.