Why Conduct Baseline Probes

The purpose for conducting baseline probes is to establish a control in an experiment. In order to know whether or not an intervention (independent variable) changed a behavior (dependent variable) you would need a reference as to how often the behavior occurs prior to starting an intervention.  

You can learn some other very important things when conducting a baseline such as what is maintaining a behavior, what rate of reinforcement is required in an intervention and if an intervention is actually clinically necessary.  

When conducting a baseline, in order to have a true measure you want to avoid teaching. However, there is always a risk of practice effects occurring, meaning that a child learns to engage in behavior from practicing it multiple times during baseline. 

Therefore, you want to collect sufficient baseline data but not too much baseline data. There is no exact set number of baseline probes needed but, you should collect baseline data until there is a stable rate of responding meaning that the respondent is consistently emitting the behavior at the same level. 

Baseline Data Paths and What They Mean


Sometimes during baseline a behavior path is ascending which means the behavior is increasing. If the behavior is a desirable behavior, this may mean that no intervention is necessary since the learner is acquiring the skill naturally. If this behavior is undesirable, even if a behavior is not stable, ethically one may want to start the intervention right away. 


Sometimes during baseline a behavior path is descending which means the behavior is decreasing. If the behavior is an undesirable behavior, this may mean that no intervention is necessary since the learner is acquiring the skill naturally. If this behavior is desirable, even if a behavior is not stable, ethically one may want to start the intervention right away. 


Sometimes a baseline data path looks variable or is up and down. This is typically caused by extraneous factors in the environment. Sometimes, you can pinpoint what is causing this variability and an intervention may not be necessary. Otherwise, you should wait for the behavior to be emitted at a stable rate before implementing an intervention. 


A stable baseline means that the respondent is emitting a behavior at the same rate and it is time to implement an intervention. 

How to Use a Baseline to Develop Experimental Control

In order for a baseline to be used to establish a functional relationship between the independent and dependent variables also known as experimental control, the follow things must occur: Prediction, Affirmation of Consequent, Verification and Replication


Prediction is when a behavior analyst predicts that once a stable baseline is established, without any intervention, the behavior will occur at the same rate in the future.

Affirmation of Consequent

During affirmation of consequent, the behavior analyst will introduce an intervention to demonstrate it causes a change in behavior.


During the verification phase, the intervention is removed. As long as it is not a learned behavior that cannot be unlearned such as tying your shoes, if there is a functional relationship between the independent and dependent variables, the rate of responding should return to baseline. 

There seems to be some controversy in the field of applied behavior analysis as to whether it is ethical to remove an intervention that is working. Some behavior analysts believe it is ethical and the only way to know an intervention is working. Personally, I believe it to be unethical to remove an intervention that is working for a learner and that a person’s individual success trumps the importance of experimental analysis. In my opinion, verification should be used in a laboratory not a clinical setting. 


During the replication phase, the intervention is reintroduced. It should have a repeatable effect on behavior. The more times that you verify and replicate an intervention, stronger experimental control is established. 

​​This article is useful for registered behavior technicians (RBT) or students who are studying to become board certified behavior analysts (BCBAs). Understanding (Applied Behavior Analysis) ABA terms is critical for both being an effective ABA therapist and passing your BCBA exam


In an effort to help you study for your BCBA exam more effectively, this post is written in a “study note” form rather than as a long form blog post. 

They are my personal study notes I am sharing with you as a gift. I am spending my time studying so they are not edited. I am grateful for your understanding in overlooking the grammar! Happy Studying! 


Cooper, J. O., Heron, T. E., & Heward, W. L. (2007). Applied Behavior Analysis (3rd Edition). Hoboken, NJ: Pearson Education.

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