Why Behaviour Occurs –

The Function of Behaviour



When carrying out behavioural assessments, we are looking to find out why the behaviour is occurring. In behavioural terms, we call this the function of behaviour. Its when we understand the why that we can then design and implement behaviour change strategies and interventions to reduce or increase certain behaviours.

As we discussed in ‘How Behaviour Works’, behaviour is a product of its environment, namely their antecedents (what happens before) and their consequences (what happens after). The most important thing to consider, however, is the consequence, which either reinforces or punishes the behaviour. The behaviour therefore serves as a function for the individual.

What are the four functions of behaviour?

There are four functions of behaviour: sensory/automatic, escape/avoidance, attention, and tangible. These functions help us to understand why the behaviour occurs.


When a behaviour serves a sensory function, it means that the individual engages in a behaviour to obtain some kind of sensory feedback. For example, hitting your head can make you feel woozy, which some people may enjoy. Many people engage in these sensory behaviours, in fact I’m sure you do quite often. How many times do you click that pen to hear that audible sound, or tap your foot on the floor for the feeling it gives you? This feedback is usually immediate and automatic, which is why it is sometimes called automatic.


This is when you engage in a behaviour to get away from, or avoid, something you find aversive. For example, taking a painkiller to get rid of a headache allows you to escape from the pain. A child may also scream and shout in order to be taken to a calm room, and away from a difficult worksheet they are struggling with, or to get away from a noisy or crowded environment.


This is when you engage in a behavior to gain the attention of others. This could be to gain praise, to get people to look at you, or even to get negative attention, such as a reprimand. For example, think of all the things you did to gain the attention of your childhood crush as a child, or to get that popular group of kids to like and accept you?


This is when you engage in a behaviour to gain access to something in particular. This could be a person, an item, or an activity. Going to the fridge when you are hungry is likely to be to gain access to food. Going to work day-in and day-out is likely to gain that paycheck. Or a child screams and shouts in the shop until you buy them that chocolate bar or toy.

What is a synthesized contingency?

Now we have discussed the four functions of behaviour, it’s important to note that its not as simple as a single behaviour serving a single function. Sometimes, that same behaviour can serve multiple functions at different times (you can shout for attention by shouting someone’s name, or for someone to leave you alone, or to gain something in particular, or simply because you like how the vibrations feel in your throat). Alternatively, you can also have multiple behaviour serve the same function at different times. You can gain someone’s attention in many different ways. By calling or shouting their name, by tapping them on the shoulder, by throwing an item across the room, they all get the same outcome.

There are also ‘synthesised contingencies’. These are when a behaviour serves two or more functions at the same time. For example, when a child hits their peer and gets sent to calm room, not only are they escaping the crowded and busy classroom, as well as their work, they are also getting to go to a quiet, calm location.

What do you determine the function of a behaviour? – The Functional Behaviour Assessment

Now you know what a function of behaviour is, and what they are, how do you actually determine what function is maintaining a specific behaviour? This is where we complete a functional behaviour assessment.

This is a process of gathering multiple different kinds of data, from various sources, analysing them all, and then comparing them to each other to hypothesise why the behaviour is occurring. The idea is that we see patterns in the data that we have, that indicates a primary function for the behaviour. We can them target interventions based on this function and support the individual to obtain the outcome they are looking for in a more appropriate way.

Each source of information we gather, as well as what we do with the information and data, are described below.

Direct Observation

What better way to see why a behaviour is occurring than to actually see it happening and observing the entire contingency. You are looking for what is happening before and after the behaviour occurs. What are they getting out of engaging in the behaviour? Do they get attention? Are they redirected to a different area, and get to escape from their environment? Do they obtain something specific afterwards?

The downside to this, however, is that this often takes the longest amount of time and may only lead to seeing a few occurrences of the behaviour over the various observational periods, especially if it’s low frequency. This is why we are not always able to rely on observational data.

ABC/Incident Analysis

In most schools and care organisations, behavioural incidents are recorded. Reviewing these records allows you to get a picture from many incidents over an extended period of time, often months or even years. This recording does, however, need to be accurate, reliable, and complete. Although this can take some time to go through, we are able to analyse this data and look for patterns over many incidents. If 90% of incidents always lead to a certain member of staff being called in to help, it is likely that the behaviour is to gain that person’s presence and attention.

In settings where recording isn’t already taking place, we would look to introduce a behaviour diary, whereby each behavioural incident that occurs is recorded over a period time. This period can be as little as a few weeks, but ideally a few months. The more the better, however pressures in the environment can always make this difficult to achieve. This recording needs to include what happens before the behaviour, the behaviour itself (in as clear and objective terms as possible), what happens after (e.g. how to those around them respond? What does the individual get out of the behaviour?), as well as general setting events, such as whether the individual slept well the night before, any changes in medication, visitors to the family home…

Indirect Assessments and Interviews

You can also get a wealth of information by speaking to people that know the individual well, such as primary caregivers. Asking questions, such as when the behaviours occur, are they more likely under certain situations, such as when it is noisy, and how they and others typically respond to the behaviour in question, can provide important information from the people that know the individual best.

There are also questionnaire tools (e.g. the QABF, the FAST, and the MAS) which aim to provide a starting point for a hypothesis on the function of a behaviour. They are questions that relate to antecedent and consequence variables, and provide a score for each function that can then be compared with other data to form a more informed hypothesis of behavioural function.

On the other hand, these are often subjective. Giving in to behaviours is the easiest way to stop them, but some people may not be willing to tell you that they do this. Also, some people have preconceived notions about why the behaviour may be occurring which may colour how they speak about it.

Review of Documentation

Lastly, we want to look at current documentation for the individual. These may not give much information about the behaviour itself, and the antecedents and consequences associated with them, but it can help you to look into and consider other factors that are important when carrying out a functional behaviour assessment. Understanding current health factors, for example, can tell you if the individual may be experiencing pain they are trying to escape from, or seizures that may impact behaviours. Medication side effects can also impact behaviours and are important to consider. Looking at the individual’s history is also important, considering potential trauma and how that may have shaped their learning history. Traumatic events are likely to create deeply rooted associations that may lead to escape or avoidant behaviours, for example.

Overall, its important to look at all this information as a whole, and then consider what it all tells you. One occurrence of a behaviour doesn’t give you the full picture, which is why it’s important to review months or even years’ worth of data to look for patterns over time.

With a clear idea of why the behaviour is occurring, its now time to design and implement behavioural change strategies and interventions.

If you would like support with behaviours that challenge, and discuss why they may be occurring (i.e. the function of the behaviour), contact us to arrange a discussion with one of our behaviour analysts and find out how we can help you.

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