Abstract

Over the last decade, research in decision-making has made remarkable advancements in understanding how the relative engagement in model-based and model-free decision-making changes with healthy aging. While we are beginning to understand the factors that affect older adults’ shift away from model-based decision-making, the exact mechanisms at play are still poorly understood. This dissertation presents findings as well as a novel theory which aims to advance our understanding of these neuro-computational mechanisms. Chapter 2 demonstrates
that, in contrast to younger adults, older adults do not benefit from more distinct probabilistic transitions between stages in a two-step decision-making task. By examining trial-by-trial neurocomputational dynamics, this first empirical paper provides evidence for age-related deficits in the ability to represent probabilistic transitions, and predict the value of upcoming choice options. Chapter 3 presents a novel theory: the diminished state space theory of human aging. This theoretical contribution proposes that older adults’ deficits in model-based learning
are due to their underlying difficulties in representing state spaces. Chapter 4 examines one of the computational explanations brought forward in this theoretical paper. Namely, that older adults’ diminished state spaces may be explained (at least in part) by their difficulties updating their internal task representation. In line with this hypothesis, results demonstrate that in contrast to younger adults, older adults show difficulties identifying outcomes that signal the need to update their internal model. Together, these findings suggest that older adults’ deficits in model-based decision-making can be explained by their diminished state space representations, which in turn may in part result from their difficulty updating their internal model during cognitive tasks. Ultimately,
this dissertation provides important insights regarding older adults’ deficits, and opens future directions for the study of age-related changes in representational abilities.