Dynamics of Spontaneous 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 were asked to either perform spontaneous word production or to let their mind wander during runs of 2 to 3 minutes, and were instructed to report thought transitions with a key press. We first validate this subjective mental event segmentation, which enables us to measure the duration of coherent thought episodes. We then 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 – but not the drift rate – negatively correlates with participants’ trait tendency for mind-wandering, highlighting the role of mental impulsivity in thought transitions.