Functional Behavior Assessments for ABA Therapy [2023 Guide]

If there is one thing that behavior analysts know, it is that behaviors always happen for a reason. While stopping at a red light or reaching into a cookie jar may be pretty straightforward, the behaviors of children, especially those with autism spectrum disorder, can be more challenging to figure out. When these challenging behaviors are harmful, disruptive, or potentially dangerous, the reasons for them must be figured out so that meaningful behavior change can be made.

Functional Behavior Assessments (FBAs) are used in applied behavior analysis (ABA) to determine why a challenging behavior is occurring, also known as the function of a behavior. The purpose of this article is to serve as a guide for parents considering or preparing for an FBA. By understanding the process and knowing how to prepare, caregivers can play an active part in the assessment and help to create meaningful behavior changes in their child.

What is a Functional Behavior Assessment for ABA Therapy?

A Functional Behavioral Assessment is a process that is common in ABA to understand why a behavior may be occurring. Behavior analysts believe behaviors occur for a handful of reasons, and they use a series of smaller assessments to determine which reason. It involves interviews, direct observation, and different types of data collection that collect information about the environment and social factors. This allows BCBAs to look at a behavior in a way that captures the whole picture. BCBAs can use all of this information to find the common conditions and triggers that are present when a behavior occurs.

Functional behavior assessments also give BCBAs the information that they need to create an individualized and effective behavior intervention plan. When the reason for a particular behavior is found, BCBAs can teach the individual with autism replacement behaviors to obtain what they want or need. For example, it may be concluded through an FBA that a child will scream to get attention from parents. Behavior analysts can then use that information to teach the child appropriate ways to ask for attention. That way, the individual is getting what they want without engaging in challenging behaviors.

A Functional Behavior Assessment Example

Functional behavior assessments for ABA therapy

Let’s look more closely at another example with Emily, a 7-year-old girl with autism spectrum disorder who engages in aggression by hitting others throughout the day. This behavior occurs both at home and at school.

The first step of the FBA process may include an interview. The BCBA may talk to siblings, parents, other family members, teachers, classroom aides, or anyone else who plays a significant role in Emily’s life. This can help narrow down reasons why a behavior occurs or determine potential triggers for the behavior. It may also determine if there is a particular person or setting that is more common. Interviews can also inform behavior analysts about past interventions and other behaviors that Emily may engage in. The interview component may or may not include a questionnaire or survey to be filled out.

The second step includes various forms of data collection. The BCBA would directly observe Emily to record information about her behavior in real time. Ideally, they would collect data in Emily’s typical settings. They may collect frequency data to determine how often the behavior occurs, scatterplot information to determine when the behavior occurs the most often during the day, or what behavior analysts call ABC data. For ABC data, information about the environment before, during, and after the behavior occurs is recorded. This allows for behavior analysts to find patterns in behavior.

With all of this information, the BCBA may determine that Emily engages in aggressive behaviors to escape from nonpreferred activities. By hitting others, she gets out of completing tasks that she does not want to do. It is found that the behavior especially occurs when transitioning from a preferred activity.

Now, the BCBA can start to create possible intervention strategies to reduce aggression. The specific strategies and interventions chosen by the BCBA (visual schedules, first-then board, break requests just to name a few possibilities) will be taught to those involved with Emily’s care to make sure that the treatment is occurring across all settings. Data on her hitting would be continuously recorded to determine if the intervention is working and if changes need to be made.

FBAs typically occur before or early into starting ABA therapy. It is not an essential prerequisite before beginning ABA therapy, but an FBA completed earlier in treatment can enhance the effectiveness of treatment.

It is important to note that FBAs can be conducted at any time. Problem behaviors may pop up throughout treatment, and sometimes the functions of established behaviors change, so it is strongly recommended for caregivers to have a continuous collaborative relationship with the behavioral team.

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Who Can Perform a FBA?

Most commonly, BCBAs or Board Certified Assistant Behavioral Analysts (BCaBAs) are the ones that conduct FBAs, although they can be conducted by others. Licensed Behavioral Analysts (LBAs), and licensed psychologists who specialize in behavior analysis may also conduct FBAs. Others may also assist in the FBA process, such as qualified ABA therapists, Registered Behavior Technicians (RBTs), and special education professionals.

When Should a FBA Be Done?

Parents considering ABA therapy for their child may find it advantageous to arrange an FBA early in the process. Initiating the assessment early ensures that the best potential behavior intervention plans can be crafted from the outset of therapy for the best possible outcomes.

It is also advisable for parents to consider an FBA when challenging behaviors appear or during significant life transitions for the child. Parents may choose to undergo an FBA preventively, even in the absence of severe behavioral issues, to gain insights into potential triggers and challenges. If a child is already undergoing ABA therapy and challenges persist, completing an FBA can be beneficial to reassess interventions.

Just as behaviors can change, the reasons for behaviors can also change. Being aware of the current functions of behavior are crucial in making interventions the best for both caregivers and the child.

How is a FBA Performed?

As described above with Emily, a functional behavior assessment involves a few different steps. It includes both indirect and direct testing to determine the function of a behavior.

Rule Out Medical Concerns

Before most FBAs begin, many BCBAs request that any medical or other concerns be ruled out, especially if the behavior has suddenly gotten worse for unknown reasons. After ruling out other possible medical or psychological concerns, they may look into previous or current records to see the history of a behavior.

Interviews & Observation

Then they will begin with the indirect and direct measurements as described above, such as interviews and data collection through direct observation. This information allows for BCBAs to make a hypothesis about the function of the behavior.

Functional Analysis

The behavior analyst may also complete something called functional analysis at the end to test and confirm their hypothesis, but this component is optional and typically requires much more time and resources. A functional analysis involves creating each of the four conditions under which the behaviors can occur. Determining under which condition The BCBA may discuss the findings with caregivers to help them collaborate in creating the best possible behavior interventions.

The intervention is then shared with all stakeholders to implement. Finally, behavior data continues to be measured to determine the efficacy of the behavior intervention.

How Long Does a FBA Take?


The duration of an FBA can take anywhere between a few weeks to a few months to complete, although most are finished after around 30 days. Several factors can influence this timeline, such as the complexity of the behavior, how much data is needed, how long the challenging behavior has been occurring, scheduling challenges for interviews and direct observation, and whether a functional analysis will be included.

It is also important to note that this assessment is not a one-time event; ongoing monitoring is crucial to ensure that interventions are always aligned with the child’s evolving needs and progress. Communication between caregivers and the BCBA can give a better idea of the progress and the expected duration of the assessment.

One FBA or Many?

FBAs are typically used to determine the function of one particular behavior, not many. Different problem behaviors may have different reasons for occurring, so it is important to complete multiple FBAs if there are multiple behaviors of concern.

Behaviors and the reasons for behavior can change, so repeating and revisiting FBAs is essential for the best possible outcomes. Repeats and revisions should especially be considered during developmental changes, transitions, or shifts in the environment. The decision to repeat an FBA is often decided after collaboration between the BCBA, parents, and other stakeholders to ensure the relevance and success of behavior interventions.

How Can I Request a Functional Behavior Assessment?

To request an FBA for a child not yet in ABA therapy, parents can begin by contacting a BCBA in the area to schedule an initial consultation. During this meeting, parents should express their concerns and share relevant medical and developmental information. They should express a desire for an FBA and inquire about the process. Following the assessment, actively engage in implementing recommended strategies to address the child’s specific needs.

How Do You Prepare for a FBA?

The first step in preparing for a Functional Behavioral Assessment is to rule out any medical concerns that may be influencing behavior. Once medical concerns are ruled out, parents may want to begin compiling information about their child, developmental history, and any other assessments that have been completed.

Parents should follow any other directions given by the BCBA before the FBA is set to begin and make sure to ask any questions or voice any concerns before the assessment begins. Finally, on the day of assessment, parents should make sure that the child is comfortable and prepared to be assessed.

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