Abstract
Kievit et al.'s target paper exemplifies a trend in recent years in psychology and neuroscience to focus on internal mental and neural processes without integrating actual behavior. We discuss the theoretical status of behavior in the context of their model, and present an extension of the model that explicitly includes behavior. Several theoretical and methodological issues relevant to integrating behavior into the model are considered, particularly the distinction between behavior as measured in the laboratory along with neural and psychological processes (proximal behavior) and behavior as measured in situ as part of ongoing daily experience (distal behavior). We conclude by describing several studies that integrate neural, psychological, and behavioral indicators and discuss how these kinds of studies can facilitate a better understanding of behavior and contribute to theory development.