What a functional assessment actually tells you

A functional behaviour assessment answers one question: what does this behaviour achieve for this person, in this setting? That is a narrower question than it first appears. It is not asking why the behaviour began, and it is not asking what condition the person has. It asks what maintains the behaviour now. The distinction matters because interventions follow function, not topography. Two children can hit for entirely different reasons — one to obtain attention, one to escape a demand — and an intervention built for the wrong function will not merely underperform. It will often make things worse. In practice, the discipline is in the data. Direct observation across conditions, recorded consistently, will usually converge on a function within a few sessions. Interviews alone will not.