Antecedent
An event, stimulus, or condition that occurs immediately before a behavior and can influence whether that behavior happens.
An antecedent is the first element of the three-term contingency, often summarized as the A-B-C model: Antecedent, Behavior, Consequence. The antecedent is whatever happens right before the behavior, including instructions, transitions, the presence of certain people, noise, demands, or the availability of a preferred item. Identifying antecedents helps teams understand the conditions under which a behavior is more or less likely to occur.
In practice, analyzing antecedents is central to understanding why a behavior occurs and to preventing problem behavior before it starts. Antecedent-based interventions modify the environment ahead of time, for example by offering choices, providing clear expectations, adjusting task difficulty, or signaling an upcoming transition, so that challenging behavior becomes less necessary or less likely.
Accurate antecedent data, recorded alongside the behavior and its consequence, is what allows a functional behavior assessment to detect patterns. When teams consistently log what preceded each incident, they can spot triggers and design proactive supports rather than relying only on reactive consequences.