Think about your own worst day last month. Someone probably said something minor to you, a request, a reminder or a bit of feedback, and it landed completely differently than it would have on a good day. Same words, same person. But you’d slept four hours, skipped lunch, and been in back-to-back stress since morning.
The comment was the trigger. Everything underneath it was the setting event. And the behaviour, whatever you said or slammed or sent, came from both.
Behaviours of concern work the same way. The trigger is what sets the behaviour off. The setting events are what set it up. Understanding both is what separates a plan that works from a plan that guesses.
The NDIS Commission’s practice guide defines both terms precisely, so let’s start there.
Setting events: the slow layer.
Setting events are the conditions or circumstances that occur at a distance from the behaviour, hours or days before, which increase the likelihood of the behaviour occurring.
“ at a distance” is the phrase that matters.
Setting events aren’t obviously visible in the moment of the behaviour. You have to know the person’s recent history to see them. The guide’s examples include: medication, routines, sleep cycles, diet, staffing patterns, physical health, the number of people in the person’s space, the daily schedule.
Notice how unglamorous that list is. Sleep. Food. Pain. Who’s on shift. Whether the house is crowded. These are the ordinary mechanics of a life, and they quietly raise and lower the odds of behaviour all day long.
Setting events explain the puzzle every support worker knows: the same demand causes an incident on Tuesday and nothing on Thursday. The demand didn’t change. The person’s capacity to absorb it did. On Tuesday there was a rough night’s sleep, a missed breakfast and an unfamiliar staff member. The tank was already low before anyone asked anything.
Internal states live here too. The guide is explicit that things like anxiety, pain and symptoms of mental health conditions are considered setting events, factors that contribute to behaviour, rather than triggers or target behaviours. They’re real, they matter, and this is the category where the assessment accounts for them.
When behaviour seems unpredictable, it usually isn’t. It’s predictable from information nobody was tracking.
Triggers: the fast layer.
A trigger, also called an antecedent, is an event or observable condition that occurs immediately before the behaviour and directly triggers it.
The guide’s examples: being asked to do something, being denied something, noise levels or certain sounds, particular places, sudden changes.
And then a rule that keeps assessments honest: triggers are observable events. They are not internal states, and they are not a reference to a person’s disability or diagnosis. “Feeling out of control” is not a trigger. “Anxiety” is not a trigger. “His autism” is definitely not a trigger. If a camera couldn’t capture it, it doesn’t belong in the trigger column. The whole assessment runs on observable events, because observable events are the only things everyone can agree happened.
Triggers are the layer most plans handle reasonably well. Data collection catches them, because they sit right next to the behaviour in time. ABC charts are built to catch them. The A column is the trigger column.
The layer plans handle badly is the one that came before.
Two layers, one behaviour.
Here’s the model in one picture. Setting events lower the person’s threshold. Triggers cross it.
On a good day, the threshold is high. The demand, the noise, the “no” all land below the line, and nothing happens. After a bad night, in pain, with strangers on shift, the threshold drops. Now the very same events land above the line.
The practice guide builds this two-layer structure directly into its expectations. Assessment data collection must cover setting events, triggers, maintaining consequences, early warning signs, and the frequency, duration and intensity of behaviour. And the guide’s model hypothesis statements name both layers separately: in one of its examples, being left alone is the trigger, while being unwell or tired are the setting events that make the behaviour more likely.
If an assessment only captured triggers, every strategy will be aimed at the moment before the behaviour, the most volatile and hardest moment to influence. The setting events, the layer where change is actually easiest, stay invisible.
Why the distinction changes the strategy.
This is the practical payoff. Setting events and triggers get different responses in a plan.
Setting event strategies are about the days, not the moments. They’re slow, boring and powerful. The practice guide gives the perfect example: if poor sleep is a setting event, the plan should include routines that support good sleep hygiene. The same logic runs everywhere. Pain as a setting event leads to medical and dental review, something the guide asks about directly. Chaotic staffing leads to roster consistency. Hunger leads to predictable meals. Crowding leads to quiet spaces and schedule changes.
These strategies never look like behaviour support from the outside. They look like a well-run life. That’s the point.
Trigger strategies are about the moments. Adjust how demands are presented. Give warning before transitions. Reduce noise. Offer choices instead of instructions. Avoid known triggers where that’s reasonable, and gradually build tolerance where avoidance would shrink the person’s life.
And the two layers talk to each other. The smartest thing a team can do with setting event information is use it to adjust the day in real time. The person slept badly? Today is not the day for the crowded shopping centre or the new activity. Lower the demands, increase the support, and the trigger never meets a lowered threshold. Some teams formalise this with a simple traffic-light system built from known setting events. That single habit prevents more incidents than any reactive strategy ever will.
You can rarely control the trigger at the moment it happens. You can almost always do something about the setting events before it does.
What this asks of data collection.
One implication before we close, because it changes what goes on the data sheet.
Standard ABC recording captures antecedents, the fast layer. To catch setting events, the recording has to widen: sleep quality, meals, health signs, staffing, schedule changes, significant events. Not forever, and not in exhausting detail. But during an assessment period, a simple daily log of these factors is what lets the practitioner find the patterns. If incidents cluster after poor sleep or on high-turnover staffing days, that only becomes visible when someone wrote both things down.
Families and support workers, this is where you’re irreplaceable. You’re the only people who know about the 3am wake-up and the skipped breakfast. The practitioner can’t see the slow layer without you.
Final words.
Triggers get the attention because they’re visible, dramatic and close to the behaviour. Setting events hide in plain sight, in sleep, pain, food, rosters and routines. But the setting events are where prevention actually lives, and they’re usually the easier layer to change.
Next time a behaviour seems to come out of nowhere, don’t ask “what triggered it?” first. Ask “what kind of day was the person already having?” The answer to the second question usually explains the first.
If a participant you support has behaviour that seems random, an assessment that maps both layers is often what turns random into predictable. That’s a conversation we’re always glad to have.
From the Insight PBS team to yours 🙂
Resources
Read the practice guide: NDIS Quality and Safeguards Commission, Behaviour Support Assessment, including Functional Behaviour Assessment: Practice Guide (2026)
Refer to Insight Positive Behaviour Support
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