ABSTRACT
This chapter provides a historical overview of functional analysis as the defining feature of behavior analysis and its centrality in ACT-based approaches. Functionalism is a core evolutionary principle that supposes the structure of something (what it looks like) interacting with its function (what it does), and behavior analysts are tasked with determining the functional processes that underly behavior. Traditional behavioral approaches have focused on immediately observable external contingencies of reinforcement; however, ample evidence suggests that complex human behavior is controlled by much more than these immediate external events. Instead, due to the impact of relational operants, ACT focuses on the co-occurrence between private behavior and public behavior that both operate within a dynamic context. Viewed in this way, a functional analysis must start by allowing for the likelihood that both private and public behavior occur and inter-relate from the historical interaction of contingencies of reinforcement. A functional approach to intervention must then attempt to alter the functions of private and public behavior while seeking to re-arrange contingencies of reinforcement that maintain psychological suffering. ACT is such a functional approach to intervention.
