ABA Therapy: Behaviours and Consequences

Read time: 4 minutes

One of the most important principles in ABA Therapy is the three-term contingency or antecedents, behaviours and consequences. Whenever we change behaviour, we have to look at the function of the behaviour. What is feeding it or keeping it going? You can read this post about the 4 functions of behaviour.

What is the Three-Term Contingency?

Each behaviour has 3 parts:

  1. Antecedent
  2. Behaviour
  3. Consequence


What happens before the behaviour. This is the signal that the behaviour should happen. In other words, it’s the trigger. In ABA terms we call the antecedent the Sd or Discriminative Stimulus. Certainly, check out this post with my list of 59 ABA definitions explained!

Antecedents cue the person that reinforcement is available if they engage in a behaviour. They can be either explicit or implicit. For example, an example of an explicit antecedent is giving an instruction. You’re telling the person exactly what to do. However an implicit antecedent can be something like how the space is laid out.


This is what the person does. That is to say, behaviours are the actions (on inactions) that the person takes after the antecedent. Behaviours must be observable and measureable. Behaviours have to pass the Dead Man’s Test. . This means that if a dead man could do it, it IS NOT behaviour.

Before we can track a behaviour we define it so that we ensure that everyone is on the same page. This is called an operational definition. In other words, we don’t want to be comparing apples to oranges! It is usually helpful to put a non-example of the behaviour in the operational definition.

Here’s an example of an operational definition:


Description: Laying on the floor, crying, yelling, throwing objects, and/or pounding fists on desk. The episode is counted if it lasts 10 seconds or more and is counted as a new incident if separated by 5 minutes or more.

Laying on the floor for 20 secondsThrowing pencil and yelling ‘no’, then re-directing to the task (lasting total of 7 seconds)
Sitting in chair and pounding on the desk without talkingSitting in the chair without working but not making any noise
Crying and yelling loudly about ‘fairness’ Crying after getting hurt
Retrieved from https://www.pps.net/cms/lib/OR01913224/Centricity/Domain/178/Example%20Definition%20of%20Measureable%20Behavior.docx on July 25, 2021.


Consequences are what happens after the behaviour that either reinforces or punishes it. Reinforcement makes behaviour likely to happen again in the future. Alternatively, punishment makes behaviour less likely to happen again. That is to say that the words we use, the things we do and even the looks we give someone after they’ve engaged in a behaviour will impact whether they happen again in the future.

Antecedents, behaviours and consequences in ABA Therapy.

Positive and Negative Consequences:

A tricky thing in ABA is the use of the words positive and negative. In plain English, positive generally implies good while negative implies bad. In ABA, when a consequence (a reinforcer or a punisher) is positive something is added to the environment . Alternatively, when a consequence is negative something is removed from the environment. As a result, people often use the incorrect meanings when talking about positive and negative reinforcers or punishers.

In conclusion:

To summarize, antecedents, behaviours and consequences are integral in changing behaviour. These are the tools that we use in ABA Therapy to be as effective and efficient as possible. Using the ABC’s of behaviour will consequently create opportunities to make long lasting improvements in people’s lives.

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