Precursor behavior and functional analysis: A brief review

Heath and his team read every precursor functional analysis paper they could find.

They wrote a short guide that tells you when to test mild behaviors instead of dangerous ones.

The review shows you can watch for early signs like hand flaps or soft vocalizations.

If these signs predict aggression or self-harm, you can run the FA on the safe behavior.

Schmidt et al. (2020) tested the guide in a clinic and proved it works in one afternoon.

Borlase et al. (2017) had already shown the same thing two years earlier, so the review pulls their data together.

Rettig et al. (2019) went further and showed blocking the early signs stops pica before it starts.

You no longer need to wait for a bite or a head-hit to learn the function. Watch for the client’s first small twitch, sigh, or repetitive hand lift. Run a five-minute test with that mild behavior. You get the same answer and keep everyone safe.

A precursor behavior is a milder, lower-intensity behavior that reliably occurs just before a more severe problem behavior, as part of a predictable response sequence. Because it comes earlier in the chain and tends to share the same function as the severe behavior, it acts as an early warning sign. Common examples include whining, pacing, or body tensing that reliably precedes aggression, or hand-flapping and vocal noise that precede self-injury.

The key features are reliability and shared function. A behavior only counts as a useful precursor if it consistently precedes the target behavior and appears to be maintained by the same consequence (for example, escape from demands or access to attention). Identifying precursors matters clinically because it gives staff a chance to intervene early, before behavior escalates to something dangerous.

A functional analysis (FA) identifies why a behavior happens by systematically testing conditions such as attention, escape, access to items, and being alone. Running a standard FA on a severe behavior like serious aggression or self-injury can be risky, because it means deliberately evoking the dangerous behavior. A precursor functional analysis solves this by arranging those same test conditions for the safer precursor behavior instead.

As this review explains, because the precursor and the severe behavior share a function, the results of the precursor FA let clinicians infer the function of the severe behavior with far less risk to the client, staff, and others. The authors propose a decision-making model for folding precursor identification into the assessment process, so practitioners can analyze severe problem behavior more safely and efficiently and then build a function-based treatment from the results.