# What is a functional behavior assessment (FBA), and how do I do one?

> Indirect, descriptive and experimental methods, common functions of behavior, and how an FBA leads to a better plan.

URL: https://theautismkit.com/guides/functional-behavior-assessment
By The Autism Kit team · Updated 2026-09-27

**Short answer:** A functional behavior assessment (FBA) identifies why a behavior happens, meaning what it gets or helps a person avoid, so the plan can teach a better way to meet the same need. FBAs combine indirect methods (interviews, questionnaires), descriptive methods (observation and ABC data), and sometimes a functional analysis, where conditions are tested systematically.

**Key takeaways**
- An FBA finds **why** a behavior happens.
- Methods: **indirect**, **descriptive** and **experimental** (functional analysis).
- Common functions: **attention, escape, access to items** and **automatic**.
- The plan should **teach a better way** to meet the same need.

## Why do an FBA?

Behavior that looks the same can happen for very different reasons. Hitting might get attention for one child and end a hard task for another. Treating the function, not just the form, leads to plans that work and last.[2]

## What methods can I use?

| Method | Examples | Strengths and limits |
| --- | --- | --- |
| Indirect | Caregiver interviews, questionnaires | Quick; depends on recall |
| Descriptive | ABC data, scatterplots, direct observation | Real context; shows correlation, not cause |
| Experimental | Functional analysis, including synthesized approaches | Shows cause; needs training and safeguards |

The first functional analysis methodology was published by Iwata and colleagues.[1] Later work showed that interview-informed, synthesized analyses can lead to meaningful improvements in everyday clinical settings.[3]

## What are the common functions?

- **Social positive**: gaining attention or access to items and activities
- **Social negative**: escaping or avoiding demands, people or situations
- **Automatic**: the behavior itself produces the reinforcement, like sensory input

## How do FBA results become a plan?

1. **Write a hypothesis**: "When X happens, the client does Y to get or avoid Z."
2. **Teach a replacement**, often through functional communication training.
3. **Change antecedents** to prevent the behavior: visual schedules, choices, breaks.
4. **Adjust consequences** so the new skill works better than the old behavior.

More in [How do I write a behavior intervention plan?](https://theautismkit.com/guides/behavior-intervention-plan)

**Visual supports as antecedent strategies.** Many escape-maintained behaviors ease when the task is predictable: a first-then board or visual schedule shows what's
  next and when the break comes.

**Safety first.** Functional analyses of severe behavior need careful planning, trained staff and safety safeguards. Follow your
  organization's policies and payer requirements.

## What can I do this week?

- [ ] Run a caregiver interview for one behavior of concern
- [ ] Collect ABC data across three sessions
- [ ] Write a function hypothesis and review it with your team

## Common questions

### What's the difference between an FBA and a functional analysis?

An FBA is the whole assessment process. A functional analysis is one method within it, where the analyst arranges test and control conditions to show what maintains the behavior.

### Do I always need a functional analysis?

No. Many FBAs rely on interviews and observation. A functional analysis is more precise and is often used when behavior is severe or other methods are unclear. It needs the right training and safeguards.

### What is an IISCA?

The interview-informed synthesized contingency analysis tests the conditions caregivers describe, combined into one test condition. It was designed to be practical in everyday clinical settings.

## Sources

1. Iwata BA, et al. Toward a functional analysis of self-injury. Journal of Applied Behavior Analysis, 1994 (reprinted from 1982). https://doi.org/10.1901/jaba.1994.27-197
2. Hanley GP. Functional assessment of problem behavior: dispelling myths, overcoming implementation obstacles, and developing new lore. Behavior Analysis in Practice, 2012. https://doi.org/10.1007/BF03391818
3. Hanley GP, et al. Producing meaningful improvements in problem behavior of children with autism via synthesized analyses and treatments. Journal of Applied Behavior Analysis, 2014. https://doi.org/10.1002/jaba.106

General guidance, not a diagnosis or treatment plan. Talk with your pediatrician or a developmental specialist about your child's care.