Functional behaviour assessment: finding out why a behaviour happens

Behaviour that worries families, such as hitting, screaming, biting, running off or throwing things, rarely comes out of nowhere. It usually does something for the child. A child who screams when the homework comes out may have learned that screaming ends homework. A child who bites their hand when the mixer grinder starts may be coping with a noise that hurts. The behaviour looks the same from the outside, but the reason, and so the right response, is completely different.

A functional behaviour assessment is the structured way a behaviour analyst finds that reason. It is built on the ABC idea at the heart of applied behaviour analysis: look at the antecedent (what happened just before), the behaviour itself (what the child actually did) and the consequence (what happened just after). Repeated across many moments, those three pieces start to show a pattern.

The result is a hypothesis, a reasoned best guess, not a verdict on the child. It should be written in plain language you can follow, and it is the foundation for everything that comes next, including the behaviour intervention plan. A plan written without an FBA is guesswork, and guesswork tends to produce responses that accidentally keep the behaviour going.

Behaviour analysts usually group the reasons behind behaviour into four broad functions. They are a starting point for thinking, not boxes to force a child into. One behaviour can serve more than one function, and the same child may hit for one reason in the morning and another in the evening.

Two cautions matter. First, 'attention-seeking' is not an insult. Wanting connection is a real and healthy need; the only question is whether the child has a better way to ask for it. Second, behaviour that suddenly appears or changes can be a sign of pain or illness: a toothache, an ear infection, constipation, poor sleep or a reaction to a new medicine. A good analyst asks about health early and will suggest you see your child's paediatrician before assuming a behaviour has been learned.

Not every difficult moment needs a formal assessment. All children have hard days, and many small problems settle with ordinary changes to routine. An FBA is worth doing when a behaviour is frequent or intense, when it gets in the way of learning, play or family life, when it puts the child or others at risk, or when the school is struggling to keep the child in class. It should come before a written behaviour plan, and it should be repeated if a plan is not working or the behaviour changes.

Safety comes before process. If your child is hurting themselves, if aggression is getting worse, or if someone has been injured, contact your child's behaviour analyst, paediatrician or psychologist quickly rather than waiting for a full assessment to be scheduled. The analyst can put a short safety plan in place first and complete the assessment alongside it.

• Self-injury, such as head-banging, biting or scratching their own skin
• Hitting, biting, kicking or pushing other people, especially if it is increasing
• Running off, at home, at school or near traffic
• Behaviour that means the child is often sent out of class or sent home from school
• A long-standing behaviour that ordinary changes at home have not helped
• A plan already in place that is not making a difference

An FBA should be carried out or supervised by a qualified behaviour analyst, such as a Board Certified Behavior Analyst (BCBA). ABA therapists may collect data under the analyst's direction, but interpreting it and writing the hypothesis is the analyst's job. The steps vary with the child and the setting, but most assessments follow a similar shape.

1. Define the behaviour in words anyone could observe and count, for example 'hits others with an open hand' rather than 'aggressive' or 'naughty'.
2. Interview the people who see it: parents, grandparents, the helper who does the evening routine, the class teacher and any shadow teacher.
3. Use questionnaires or rating scales where useful, to gather the views of several adults in the same way.
4. Observe the child directly, at home, at school or in sessions, recording what happens before and after each episode.
5. Look for patterns: times of day, places, people, tasks, noise, hunger, tiredness, and what usually follows.
6. Write a hypothesis about the function, and share it with the family in plain language.
7. Where needed, test the hypothesis carefully before building the plan.

That last step sometimes involves a functional analysis, in which the analyst deliberately sets up a few short, controlled situations to see which one the behaviour responds to. It is a specialised procedure that needs a trained analyst, a clear safety plan and your informed consent, and it is not something to try yourself at home. Many assessments reach a confident hypothesis without one.

You see your child across the whole week: the rushed mornings before the school van, the hungry hour after school, Sunday visits to relatives, the evening the power goes and the fan stops. An analyst sees a slice of that. Your observations fill in the rest, and they often hold the clue that makes the pattern make sense.

The most useful thing you can bring is honest detail about what usually happens straight after the behaviour, without worrying about being judged. If Dadi gives a biscuit to stop the crying, or the tablet goes back on to end a fight, say so. Every household does this; it is how adults get through a hard moment. Knowing it helps the analyst understand what the behaviour is achieving for the child.

Short written notes over a week or two are far more useful than memory. The guide to recording behaviour at home with ABC notes shows how to write them quickly and what to leave out. It also helps to mention the context around each hard moment.

• When and where the behaviour happens most, and when it almost never happens
• What usually comes just before it, and what adults usually do just after
• Changes in sleep, eating, health or medicine
• Changes at home or school: a new helper, a new teacher, a house move, a new sibling, exams, a festival week
• How your child communicates, in each language spoken at home
• What your child loves, and what calms them

Once the assessment is done, you should understand the result. If you do not, keep asking until you do. Clear answers to these questions are a good sign; vague ones are a reason to ask again.

• Which behaviour exactly was assessed, and how was it defined?
• Where and when was data collected, and by whom?
• What is the hypothesis about the function, and how confident are you?
• Were pain, illness and sensory difficulties considered?
• What will my child be taught to do instead, and how will that meet the same need?
• How will the school and the rest of the household be involved?
• How, and when, will we know whether the plan is working?

An FBA should lead to understanding and teaching, not to punishment. Autistic adults have criticised ABA for treating harmless behaviour as a problem and for overlooking the distress a behaviour may be signalling. A good assessment takes those concerns seriously. It focuses on behaviour that causes harm or genuinely gets in the child's way, leaves harmless stimming alone, does not set goals such as forced eye contact, and treats the child's needs, including the need to say no, as real.

The plan built from it, described in our guide to what a good behaviour intervention plan contains, should be positive, practical and reviewed against data you can see.

Special Minds provides ABA therapy at home, at school with the school's agreement, online with parent coaching and at a centre, and every programme is designed and supervised by a BCBA. Where behaviour is a concern, the analyst's first step should be to understand it, and a vetted shadow teacher or special educator can record observations at school or home under the analyst's direction. You can ask for the supervising BCBA's name and check the credential on the BACB's public registry. The guide to ABA therapy in India explains how a programme starts.