The Three-Term Contingency: How A, B, and C Fit Together

The three-term contingency (antecedent-behavior-consequence) links what comes before a behavior, the behavior, and what follows. It is often shortened to "ABC." Some analysts also call it stimulus-response-stimulus, or simply the operant.

This idea sits at the root of how behavior analysts think. It is a way to see behavior as part of a chain of events, not a thing that happens alone. Speakers in OpenCEU talks use it, question it, and stretch it. Here is what each one adds.

What the three terms mean#

Each letter stands for one part of a moment. The "A" is the antecedent. That means whatever happens right before the behavior. The "B" is the behavior. That is what the person does. The "C" is the consequence. That means whatever happens right after the behavior.

The power of the model is in the links between the parts. A consequence can make a behavior more likely to happen again. When that happens, we call it reinforcement, which simply means the behavior grows. The antecedent then becomes a cue. It tells the person that the same behavior may pay off again.

So the three terms are not just a list. They form one unit. You cannot fully understand the behavior without the parts on each side of it. Many teams also write these three parts down as they happen. That data collection method is often called ABC data, and it is its own topic. This page stays focused on the idea behind it.

A real example from the session room#

Anlara Hoskins walks through a simple case in her talk for RBTs. An RBT is a registered behavior technician, the person who works with clients day to day. In her example, another child walks into the room. The client starts screaming. Then the other child leaves.

in this abc three term contingency the antecedent of the clients entering the room behavior is your client is screaming The other client is now leaving the room and your clients behavior of screaming is increasing

From the talk — Anlara Hoskins

Hoskins points to the last part as "the key." The screaming is growing over time. That tells you the other child leaving is working as reinforcement. The client screams because screaming gets the result they want.

She says this is something to tell your BCBA, the supervising behavior analyst. The BCBA might run a functional behavior assessment. That is a careful look at why a behavior happens. From there, the team can teach a replacement behavior. For example, the client could learn to ask the other child to leave. Hoskins covers how reinforcement works in more depth in Bite-Size Behavior Analysis: Behavior Analytic Definitions of Reinforcement & Punishment. Her point is that RBTs are the eyes and ears on the ground.

The operant: stimulus, response, stimulus#

Mark Malady starts his talk on skill assessment with the basics. He asks a simple question first. What is the subject matter of our science? His answer is the interaction of a person and their environment.

our most basic construct is stimulus response stimulus or the operant.

From the talk — Mark Malady

This is the same three-part unit with different labels. A stimulus is anything in the world a person can sense or react to. The first stimulus sets the stage. The response is what the person does. The second stimulus is what the world gives back.

Malady uses this unit to frame how we should assess skills. If the subject is interaction, then a skill test should look at the person and the setting together. It should not only score what the learner does in a vacuum. He goes on to warn about "normalization agendas" hiding in assessment tools. That phrase points to tools that push learners toward one standard way of acting. He argues for flexible assessment that still keeps the tool accurate. This view grows straight out of how he defines the basic unit.

Why the B in the middle can mislead#

Malady is open about a problem he sees with the ABC label. He thinks the letters steer people the wrong way.

I'm really not a fan of the ABC metaphor because the B in the middle pulls our attention that behavior is action. And that turns our science into a practice that's focused on action rather than interaction.

From the talk — Mark Malady

His worry is about focus. When "B" sits in the center, it looks like the star of the show. People may start to treat behavior as only what the client does. The setting and the results then fade into the background.

Malady wants the opposite. He reminds his audience that we are talking about responses in interaction with an environment. The parts on each side matter as much as the middle. He also names a model he likes even more. It comes from a school of thought called interbehaviorism. In that model, the organism sits on one side and stimulus objects sit on the other. The event is what happens between them.

This is not a rejection of the three-term contingency. Malady still calls stimulus-response-stimulus our most basic construct. He is pushing back on the shorthand, not the science.

What three terms can leave out#

Eric Soltysik raises a different concern in his talk on working with caregivers. He uses a four-step tool he calls the KIND framework. One step asks, "What don't I know?" Here he points to a gap in the classic model.

what we have seen. at the typical three-term. contingency doesn't necessarily always give us the full picture of what's going on with her. client

From the talk — Eric Soltysik

Soltysik names setting events and environmental factors as the missing pieces. Setting events are conditions that change how strong a consequence feels. They may happen long before the antecedent. He calls these factors "so vitally important." Without them, he says, we may get only "a tiny snippet" of what is really happening.

So for Soltysik, the three terms are a starting point. They are not the whole story. A tidy ABC chain can still miss the bigger forces at work in a client's day.

Building the bigger picture#

Both Malady and Soltysik reach for more context, but from different angles. Their ideas fit together well.

Malady widens the view across time. He says we must also think about selection at more than one level. He lists biological selection and cultural selection. He adds the person's history of reinforcement, their genetic makeup, and their current environment. In his words, "Our subject matter is rich. It is deep. It's very complex."

Soltysik widens the view across people. His next KIND step asks, "Who might know it?" He means which person has the expertise to fill the gap. That could be the RBT or the behavioral health technician. It could also be a caregiver, a doctor, an occupational therapist, or a speech therapist. Then he asks what the person actually needs. He contrasts that with simply forcing compliance, which means getting a client to obey.

He keeps one rule firm through all of this. Data guides the work. "Show me the data," he says. The three-term contingency gives that data a shape. The wider context helps you read it well.

What the research says#

Research keeps testing how far the three-term unit can reach. One paper asks what differential-outcomes research means for our behavioral units (Catania, 2025). Differential outcomes means each correct response earns its own kind of result.

Other studies look at where teaching happens in the chain. One compared feedback given after a task with feedback given before it (Aljadeff-Abergel et al., 2017). In ABC terms, that moves feedback from consequence to antecedent.

A study of children with Naming found demonstrations worked faster than consequences alone (Hranchuk et al., 2019). Naming is a skill where a child learns words just by hearing them. That result puts weight on the antecedent side.

The unit also shows up in training. One paper describes behavior change projects in college behavior analysis courses (Armshaw et al., 2021). It uses a constructional approach. That means building new skills rather than only cutting problem behavior.

FAQ#

What does ABC stand for in behavior analysis? ABC stands for antecedent, behavior, and consequence. The antecedent comes first, then the behavior, then the result. Together they make the three-term contingency.

Is the three-term contingency the same as the operant? Yes, in the way Mark Malady uses the words. He calls stimulus-response-stimulus "the operant" and our most basic construct. The labels differ, but the three-part unit is the same.

Why do some analysts say three terms are not enough? Eric Soltysik notes the three terms can miss setting events and other environmental factors. Mark Malady adds history, biology, and culture. Both want a fuller view of the person in context.