Uncovering the contents and dynamics of the stream of thought

Abstract

The mind can access a vast landscape of thought. Our thoughts frequently wander away from the here and now to explore this landscape. In this dissertation, I examine the contents and dynamics of spontaneous thought to gain insight into its structure and function. In Chapter 1, I propose a theoretical framework that frames spontaneous thought as an unconstrained memory process. In this framework, semantic memory scaffolds episodic simulation to form the contents of thought. Our minds explore memory space in a clustered fashion, with thoughts focused within a particular topic until it is time to find new memories to explore. At that point, a drifting context shaped by one’s current state helps determine which portion of memory space to explore next. In Chapter 2, I leverage predictions from this framework to test the function of spontaneous thought. I show that the dynamics of spontaneous thought prioritize episodic detail: the first thought in a new topic contains the most episodic detail, which decreases with each subsequent thought until it is time to find a new topic. Thoughts also prioritize goal-related content in a similar manner, although this content begins to increase in the thoughts immediately preceding a topic jump. These findings suggest that spontaneous thought helps optimize memory storage by replaying episodic details and aids in our ongoing goal pursuits by keeping current concerns in mind. In Chapters 3 and 4, I use sociality as a test case for the role of the external environment in shaping thought. Across different social contexts in the lab (Chapter 3) and in the real world (Chapter 4), I find that social spontaneous thought reflects the amount of social information in the environment, consistent with the hypothesis that spontaneous thought helps process incoming social information. Taken together, this work shows that spontaneous thought serves to both optimize memory and attend to current concerns. The external (social) environment and internal state can both affect the extent to which these functions are expressed in spontaneous thought.