Why does a child call out in class? Why does an adult check their phone the second a notification pings? These everyday moments aren’t random. Behavior has a pattern, and one simple tool from Applied Behavior Analysis (ABA) helps us see it: the three-term contingency.
At its heart, this is about three parts: what happens before, what we do, and what happens after. Simple words, but they explain a lot.
Antecedent – what comes before
Think of the green traffic light. It tells you it’s safe to drive forward. Or a teacher’s question—an invitation for a student to raise their hand. These signals matter because of history: in the past, acting on them “worked.”
Behavior – the action
This is the thing we actually do. A child blurts out, an adult sends an email, someone heads to the gym.
Consequence – what follows
And then comes the result. This is what shapes whether we’ll do it again. Sometimes it’s reinforcement (something good follows, so we repeat it). Sometimes it’s punishment (something unpleasant follows, so we stop). And sometimes it’s extinction (what used to “work” no longer pays off, so the behavior fades).
A classroom example
Here’s how the three-term contingency looks in action:
- Problem pattern
- Antecedent: The teacher assigns independent work.
- Behavior: The child shouts, “Help!” across the room.
- Consequence: The teacher walks over and provides help.
- Result: Shouting is reinforced, because it gets attention and support.
- Replacement pattern
- Antecedent: The teacher assigns independent work and places a “help” card on the desk.
- Behavior: The child holds up the card when stuck.
- Consequence: The teacher responds quickly to the card, but not to shouting.
- Result: Holding up the card is reinforced with attention and help, and over time it replaces the shouting.
Both patterns are three-term contingencies. In the first, shouting “works.” In the second, the child still gets what they need, but in a way that’s more helpful for everyone.
But are we just robots?
Talking about behavior this way can sound mechanical, as if we’re nothing more than stimulus-response machines. Of course, that isn’t true. We all have thoughts, feelings, memories, and private experiences. The three-term contingency doesn’t deny those – it just gives us a practical way to notice patterns in what we can see and change. That’s why it’s so useful for parents, educators, and anyone who works with people.
Why this matters
Children and adults alike are constantly learning which actions “work” in their environments. Sometimes this learning is conscious – like practicing piano scales. Often it’s unconscious – like reaching for your phone without realizing. For parents and educators, this matters because it means behavior can be guided. We can reinforce the things we want to see more of, reduce the pay-off for harmful behaviors, and pay attention to when we’re accidentally using punishment.
The point isn’t that behavior is simple. It’s that the ABC framework gives us a clear, workable way in. And with it, we can create environments that support safety, growth, independence, and dignity for the children and adults in our care.
