Towards a Normative and Mechanistic Account of Cognitive Fatigue

Abstract

Cognitive fatigue and boredom are two phenomenological states that reflect overt task disengagement. In this dissertation, we present a rational analysis of the temporal structure of controlled behavior, which provides a formal account of these phenomena. We suggest that in controlling behavior, the brain faces competing behavioral and computational imperatives, and must balance them by tracking their opportunity costs over time. We use this analysis to flesh out previous suggestions that feelings associated with subjective effort, like cognitive fatigue and boredom, are the phenomenological counterparts of these opportunity cost measures, instead of reflecting the depletion of resources as has often been assumed. Specifically, we propose that both fatigue and boredom reflect the competing value of particular options that require foregoing immediate reward but can improve future performance: Fatigue reflects the value of offline computation (internal to the organism) to improve future decisions, while boredom signals the value of exploration (external in the world). We demonstrate that these accounts provide a mechanistically explicit and parsimonious account for a wide array of findings related to cognitive control, integrating and reimagining them under a single, formally rigorous framework. We follow this theoretical work with a behavioral and neuroimaging study that aims to explicitly test the mechanistic claim created by cognitive fatigue. The proposal of this new experimental paradigm is especially important with `ego depletion' and its associated experimental paradigms falling out of favor. Chapter 2 introduces the theoretical framework and is separated into three parts, one for fatigue, one for boredom, and one for mind-wandering. The subsequent chapters evaluate the fatigue hypothesis. Chapter 3 introduces a behavioral study and its corresponding analyses. Chapter 4 discusses the neuroimaging portion, aiming to establish a link between replay and default mode activation. Chapter 5 concludes by placing this piece of work into a broader research agenda.