If the interview usually leads to differentiated functional analyses, why not simply conduct the interview and forgo the analysis?

There are three reasons to conduct the analysis even when the interview provides fairly straightforward information regarding the specific reinforcement contingencies likely controlling problem behavior.

1. Although the interview may help you discover the specific reinforcement contingencies that may be influencing problem behavior, the analysis is needed to demonstrate the sensitivity of problem behavior to those factors. There is a sort of professional humility that is evident when behavior analysts hold off on claims of controlling variables until they have seen those variables actually control behavior. By conducting the analysis, you are holding yourself to a reasonable yet scientific standard of proof.

2. By conducting the analysis, you are essentially creating a baseline from which to evaluate treatment. Stopping at the interview leaves you either without a baseline of problem behavior for your treatment evaluation or relying on some sort of naturalistic baseline, which is usually neither stable nor reliable and thus incapable of assisting you in making decisions regarding the efficacy of your function-based treatment. In other words, the test condition of the analysis yields a stable and sensitive baseline from which to evaluate your function-based treatment.

3. This baseline is also a properly motivating set of conditions to teach skills. When you have identified condition under which a child is willing to engage in severe self-injury or aggression, you have identified (a) a powerful condition to teach a child to mand, or more specifically, learn functional communication responses, (b) a challenging condition to teach that same child a skill set relevant to tolerating delays and denials of reinforcers, and (c) a condition to promote compliance with adult instructions during delays. In other words, the analysis sets you up to develop a skill-based treatment capable of meaningful outcomes.