Dynamics of the stream of thought: insights from an accumulation-to-threshold model.

The dynamics of the stream of spontaneous thoughts has been the object of increasing research in recent years. Here, we study the timing of transitions from one coherent thought episode to the next as one aspect of such dynamics. Participants either vocalized freely generated words or allowed their minds to wander during 2- to 3-min runs, and were instructed to report thought transitions by pressing a key. We first validate this subjective mental event segmentation, which enables us to measure the duration of coherent thought episodes. We then turn to model comparison to show that the timing of thought transitions is best explained by an accumulation-to-threshold mechanism. We further find that the threshold of this accumulation negatively correlates with participants' trait tendency towards disorganized thought. We speculate about the nature of the accumulated information and emphasize that individual variability in transition thresholds underscores the role of mental impulsivity in thought transitions.