Effects of familiar versus unfamiliar therapists on responding in the analog functional analysis.

The team ran two sets of functional analyses on four children with developmental delay. One set was run by the child’s everyday caregiver. The other set was run by an unfamiliar lab experimenter.

Everything else stayed the same—same room, same toys, same test conditions. The only change was who sat across from the child.

Three of the four kids acted differently when the caregiver ran the session. Some showed more problem behavior. Some showed less. One child’s behavior stayed the same.

The different response patterns could lead to different function conclusions if you only looked at one set of data.

Holehan et al. (2020) and Irwin Helvey et al. (2022) also tweak FA details. They changed how contingencies are arranged, not who delivers them. All three studies show small setup changes can shift outcomes.

Bamise et al. (2026) extends the idea overseas. They prove you can train new staff anywhere to run FAs. Together with Matson et al. (2004), the message is clear: both the person and the procedure matter.

Burren et al. (2025) pools 47 studies and confirms FA-based treatments work best. Their mega-review includes caregiver-run FAs, so your results can still guide strong interventions even if the pattern looks different.

If you run an FA with only strangers, you might miss how the child acts at home. If you run it only with Mom, you might miss how they act with teachers. Best practice: run one session with a familiar adult and one with a neutral therapist, then compare. This quick check keeps your function guess honest and saves treatment time later.