While functional behavior assessment (FBA) has been a part of special education law and embedded in Individuals With Disabilities Education Act (IDEA) since 1997, a precise definition of what actions or processes constitute a legal FBA has never been adequately addressed in the law. This article provides an overview of the underlying logic of FBA leading to effective function-based intervention. When focusing on a simplification of the logic behind FBA, there are three big ideas that serve as a foundation for considering the intersection of effectiveness and practicality: function matters, FBA requires repeated observations of behavior, and the only purpose of an FBA is to develop an effective intervention. These big ideas are discussed, leading to a conclusion as to how logic and simplicity must share priority in the process.
