Functional Behavioral Assessment in ABA Therapy

Reviewed by:
Hannah Andreasen

December 28, 2022

A functional behavioral assessment (FBA) is a set of strategies used to help understand the purpose of certain behaviors that may be creating safety concerns or impacting a child’s development. Once the reason for the behavior is discovered, a more effective intervention plan can be made. FBA is a common strategy used in applied behavior analysis (ABA). 

FBA is often combined with other strategies like functional communication training (FCT), stimulus control, extinction, and differential reinforcement in ABA to address behaviors in children with autism.

What Is Functional Behavioral Assessment? 

FBA is a method used to understand the reasons behind why a child may perform a certain behavior. FBA can be used for children and adolescents from the ages of 3 to 15. This strategy can be used in schools, community centers, or at home. An FBA is performed by a multidisciplinary team of people from different fields, such as ABA therapists, teachers, parents, special educators, and the child. 

Several studies have shown that this method is effective and it is considered an evidence-based practice by the National Professional Development Center on Autism Spectrum Disorder.

How Is Functional Behavioral Assessment Used in ABA Therapy?

FBA is a useful tool that ABA therapists can use to discover the reasons behind a behavior. 

There are four steps for a successful FBA.

Step 1: Define the Target Behavior

An ABA therapist will work with a team that includes parents, teachers, and other professionals to identify the target behavior. The behavior chosen for the FBA usually interferes with optimal development, learning, or achievement. The behavior should be described in a specific and objective way. 

Even if there is more than one challenging behavior, only one specific behavior will be chosen as the target behavior for the FBA. 

An FBA may target behaviors such as:

  • Communication difficulty
  • Behaviors that put the child or others at risk (e.g. biting, hitting)
  • Stimming that is excessive or harmful
  • Disruptive behaviors (e.g. yelling, hitting)
  • Escape-motivated behaviors (e.g. running out of the classroom)

Step 2: Gather and Analyze Information

Once the target behavior is identified, the team will gather information and data about the behavior. The goal is to use this information to answer key questions about the behavior, such as:

  • What happens right before and right after the behavior occurs? 
  • What are the environmental factors when the behavior occurs? 
  • Where, when, and how long does the behavior occur?
  • Where does the behavior not occur?
  • How often does the behavior occur?
  • Who is around when the behavior occurs?

An ABA therapist can use different methods to gather this information. 

Indirect Functional Assessments

An indirect functional assessment uses information from people who observe the child’s behavior, including parents, caregivers, and teachers. The therapist may use questionnaires, interviews, and rating scales to collect data on your child’s behaviors. 

One example is the Functional Analysis Screening Tool (FAST). This questionnaire can be taken by people who know the child well. It uses 16 questions to help discover if there is anything happening before or after the behavior that might be influencing it.  

Descriptive Assessments 

Descriptive assessments, also called observational functional assessments, involve the ABA therapist directly observing the child in their natural environment. The ABA therapist will watch the child and record what happens before, during, and after the target behavior. 

Functional Analysis 

A functional analysis involves an experimental test to determine the possible reasons that drive the target behavior. The ABA therapist will observe the child in different conditions to help determine the motivation for the target behavior and compare this to what the child does in their normal environment. 

This type of experiment can help answer the following questions:

  • Does the target behavior occur to get away from tasks, activities, or demands?
  • Does the target behavior occur to get attention from someone?
  • What does the target behavior look like when the child is alone in a room with no other activities or toys?
  • Does the target behavior occur to receive a tangible item, person, or activity?

Step 3: Find the Reason for the Behavior

After all the information is collected, the team will make an educated guess, or hypothesis, as to why the behavior is happening. 

The hypothesis should include:

  • What happens before, during, and after the target behavior
  • A description of the target behavior
  • The function of the target behavior

The hypothesis should be tested over the course of several days to weeks by adding activities or situations to therapy that increase the chances of the interfering behavior occurring.

Step 4: Make a Plan

Once the team has discovered the purpose of the target behavior, the ABA therapist can develop a behavior intervention plan (BIP). This will use evidence-based practices that help limit how often the interfering behavior occurs and replace it with appropriate behaviors instead. 

The BIP will include:

  • How to prevent the interfering behavior from occurring
  • Teaching and increasing the new appropriate behavior 
  • Increasing opportunities for your child to use their new behaviors in other situations 

The team will continue to monitor the child’s progress after learning their new appropriate behaviors. The ABA therapist may provide tools to use, including forms to fill out describing when interfering behaviors occur, how long they last, and what strategies were used to increase use of the appropriate behavior. 

If the child continues the target behavior instead of appropriate ones, the ABA therapist may recommend a new evidence-based practice and redevelop the BIP.


FBA is an evidence-based method used in ABA therapy to understand why a child may be performing a certain behavior. FBAs involve a team of people who are familiar with the child and the target behavior to identify and address behaviors that may create safety concerns or interfere with the child’s ability to learn.

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