When the Nervous System Speaks: Understanding Sensory Behaviour in Autism

Blog #13 | When Behaviour Speaks Louder Than Words series

TL;DR

Sensory behaviour is driven by the nervous system's need to seek or avoid input  and it's the hardest function to address because it doesn't follow the script. The same trigger (like a fire alarm) can produce calm in one child and crisis in another. Sensory-seeking behaviours like spinning or humming are often regulation strategies, not disruptions. Sensory avoidance can be traced to genuine overwhelm, or to learned fear responses from earlier experiences. What works: observation, environmental modification, and micro-dosing exposure in predictable, low-stakes conditions. Start with curiosity, not correction.

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I taught a student who drummed. Constantly - on the desk, on his knees, on whatever surface was within reach. He sang too, sometimes under his breath and other times a solo performance. His own private soundtrack running alongside whatever was happening in the classroom - completely elsewhere.

Managing the behaviour was one thing. But watching him was another, because I could see his potential clearly. He was bright. He was capable. He had skills well above his age. The drumming and singing were pulling him away from all of it, into a world where the classroom's demands simply couldn't follow him.

I'll be honest: there were days I was at the end of my rope. Because this wasn't a behaviour I could redirect my way out of, or solve with a visual schedule. His nervous system had found its safe place, and it did not want to leave.

That's what sensory behaviour can look like from the inside of a classroom. Not over-the-top chaos but something quieter and harder to name. A child who has found a way to regulate that works for him, and a teacher trying to figure out how to reach him anyway.

Overview

This is Post 3 in the When Behaviour Speaks Louder Than Words series, where we've been exploring the four functions of behaviour using the SEAT framework: Sensory, Escape, Attention, and Tangible. In Post 1 we introduced the framework and in Post 2 we went deep on escape and avoidance. Today we're focusing on the S: sensory behaviour.

Sensory behaviour is, in my experience, the hardest function to address, not because it's the most dramatic, but because it doesn't follow the script. Unlike escape behaviour, which usually has a clear trigger (a task, a setting, a demand), sensory behaviour can seem random from the outside. It can look like something else entirely. And the same sensory trigger can produce completely opposite responses in two different children.

We'll look at both sides of that coin today: sensory seeking and sensory avoidance, and what regulation actually looks like when you're living inside a nervous system that processes the world differently.

What sensory behaviour actually is

When we talk about sensory behaviour in autism, we're talking about behaviour that is driven by the nervous system's need to either get sensory input or get away from it. This is sometimes described as sensory seeking versus sensory avoidance, and understanding which one you're looking at changes everything about how you respond.

A child who seeks sensory input is trying to fill a need. Their nervous system is under-stimulated in some way, and the behaviour such a spinning, jumping, rocking, humming, pressing into things, seeking touch (hug or squeeze) - is how they regulate. It feels good. It calms the system. It's not random; it's purposeful, even if it doesn't look that way from the outside.

A child who avoids sensory input is trying to escape an experience that feels overwhelming or even painful. Sounds that seem ordinary to us like a timer going off, a classroom buzz, a change in background noise, can hit a sensitised nervous system like a jarring alarm. The behaviour that follows (shutting down, covering ears, melting down, fleeing) isn't an overreaction. It's a proportionate response to what that child is actually experiencing.

And then there's a third layer that doesn't always get named: sensory behaviour as escape. Not necessarily an escape from a task or a demand but escape into a sensory world that feels more appealing than the one the child is being asked to inhabit. Like my student who drummed constantly, he wasn't seeking stimulation for its own sake. He was using it to exit. His nervous system had found a private place, and the drumming was the door.

The tricky part? Some children do both, in different contexts, with different inputs. And some behaviours that look like one thing are actually the other.

From My Classroom

The child who spun and why I stopped trying to stop it

I had a student who would spin during group activities. Not endlessly, he'd do a few rotations and then rejoin whatever was happening. Other children noticed. Adults noticed. The instinct, in a busy classroom, is to redirect: come sit down, we don't spin during circle time.

But the more I watched him, the more I realised what was happening. When he spun, his nervous system was expressing something. Not frustration, not defiance but something closer to delight. He spun when he was excited, when the activity was enjoyable, when he was engaged. It was his nervous system's version of clapping. He wasn't necessarily disrupting. He was regulating. And he always came back.

This is what I mean when I say sensory behaviour doesn't follow the script. You might expect a child with sensory needs to struggle during loud, busy activities. But sometimes the child who spins during circle time is the one who's most present in the room.

When the environment changes everything

Another student I worked with had been steady behaviourally, emotionally, in terms of engagement. Then things shifted. He became harder to reach, more reactive, more dysregulated across the board. Nothing obvious had changed at school.

It was his parents who eventually filled in the gap. The family had been temporarily relocated due to a house renovation. They hadn't mentioned it because, as his parents put it: "We didn't think it would affect him so much."

It had affected him enormously.

For children on the autism spectrum, environmental change isn't just an inconvenience - it's a sensory and neurological event. A new space means new sounds, new smells, new light quality, new textures underfoot. A new sleep environment. A new route to school. None of these things are dramatic in isolation, but for a nervous system that relies on predictability to stay regulated, they add up quickly.

The takeaway here isn't that we need to bubble-wrap these children's environments. It's that when behaviour shifts suddenly, we need to ask: what has changed? Not just in the classroom but also at home, in the neighbourhood, in the family's routine. The answer is often there, waiting to be found.

Sound: the same trigger, two opposite responses

This is where I want to stay for a moment, because I think it illustrates something important about how differently sensory processing can work from child to child.

Take a fire drill. For most children,  even those with sensory sensitivities - the alarm is unpleasant but manageable. With preparation, pre-teaching, and some noise canceling headphones, most get through it. Some barely react at all.

I once had a parent asked me how her son had handled the fire drill. I told her he'd been calm, collected, one of the easiest children in the room to manage during the whole event. Without hesitating, she said she'd actually hope he would show more urgency to get out of the building.

It was a striking conversation. From a safety standpoint and honestly, from a classroom management standpoint, a child who stays regulated during a fire drill is exactly what you want. But she was raising something real: a child who has no reaction to a genuine alarm signal is worth paying attention to, for different reasons.

A few years later, I had another student, for whom the sound of a timer was enough to send him into full dysregulation. Not the fire drill alarm but a timer. The kind teachers use constantly throughout the school day. I also learned that he also reacted intensely to the doorbell.

What made this case so interesting and so difficult was what didn't bother him. Metro doors closing. The sounds of buses and trains. Environmental noise that, to some sensory-sensitive children, is genuinely overwhelming. None of that registered as threatening. Only certain sounds did.

Why? Possibly because those sounds were unpredictable. Possibly because a timer meant a transition was coming, and transitions carried their own weight. But there was another possibility I kept coming back to: earlier in the school year this student had shared a classroom with a peer whose behaviour was highly unpredictable, including blood-curdling screams that came without warning. It's very possible that those early experiences had primed his nervous system to treat sudden, sharp sounds as a threat signal, regardless of their actual volume or context.

Whether or not that was the cause, what I observed was a nervous system that had learned to be afraid of certain sounds and that learning was real, even if its origins were unclear.

What gradual exposure actually looks like

We didn't try to power through. We didn't expose him to the timer and wait for the reaction to extinguish. We started by removing the sound entirely.

I used the timer on the smart board which had a visual component when it reached zero, confetti appeared on screen. For a while, that was all we used (this bothered some of my students but sacrifices had to be made). No sound at all, just the visual. Even then, it took him a while to not react to a soundless timer. Eventually, he knew time was ending. He could prepare.

Then, very gradually, we introduced sound. Not at full volume but barely audible at first. Week by week, we increased it in tiny increments. Crucially, we also added a verbal warning before the timer went off: "Two more minutes." Predictability was the medicine.

By the end of the school year, he could tolerate the timer at a volume loud enough to alert the whole class. Not without awareness, but without crisis. The nervous system had learned, slowly and safely, that the sound wasn't a threat.

This process of what I'd describe as micro-dosing exposure in a calm, predictable environment is painstaking. It requires consistency, patience, and a team that agrees on the approach. But it works in a way that forcing the exposure never does.

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The honest truth about sensory behaviour

Sensory behaviour is, in my experience, the hardest of the four functions to address. And I say that not to discourage you but because I think it's important to name it.

With escape behaviour, you can often identify the trigger and modify the demand. With attention-maintained behaviour, you can adjust how you respond. Sensory behaviour is different because it lives in the body. You can't reason a nervous system out of what it needs. You can't explain to a child why the timer shouldn't bother them. And you often can't even fully understand why certain inputs land the way they do because, as with the sound-sensitive student, the history of the nervous system isn't always visible.

What you can do is observe carefully. Ask questions. Change the environment before you try to change the child. And hold the line on this: what looks like misbehaviour is often regulation. What looks like overreaction is often a proportionate response to a genuine sensory experience.

The student who showed delight through spinning wasn't disrupting. He was coping. The student who drummed constantly and cycling through behaviours wasn't acting out. He was trying to find equilibrium. The student who fell apart during a renovation wasn't being difficult. His nervous system was absorbing an enormous amount of change, and his behaviour was the evidence.

When we start from that place of curiosity instead of correction, we get a lot further.

One takeaway

If you take one thing from this post, let it be this: sensory seeking and sensory avoidance are two sides of the same coin. The child who seeks input and the child who flees from it are both trying to regulate. The question to ask isn't how do I stop this behaviour? Rather, it's what does this nervous system need right now?

Bridge to Post 4

Next week, we move to the A and T in SEAT: Attention and Tangible behaviour. These are the functions that often feel the most interpersonal  and they come with their own set of misconceptions about what a child is "really" doing when they act out for attention. Spoiler: the answer might surprise you.

See you next Thursday!

Sources & Further Reading

• Baranek, G. T., David, F. J., Poe, M. D., Stone, W. L., & Watson, L. R. (2006). Sensory Experiences Questionnaire: Discriminating sensory features in young children with autism, developmental delays, and typical development. Journal of Child Psychology and Psychiatry, 47(6), 591–601. https://doi.org/10.1111/j.1469-7610.2005.01546.x

  
  

• Case-Smith, J., & Arbesman, M. (2008). Evidence-based review of interventions for autism used in or of relevance to occupational therapy. American Journal of Occupational Therapy, 62(4), 416–429. https://doi.org/10.5014/ajot.62.4.416

  
  

• Marco, E. J., Hinkley, L. B. N., Hill, S. S., & Nagarajan, S. S. (2011). Sensory

  processing in autism: A review of neurophysiologic findings. Pediatric Research, 69(5 Pt 2), 48R–54R. https://doi.org/10.1203/PDR.0b013e3182130c54

  
  

• Schoen, S. A., Miller, L. J., Brett-Green, B. A., & Nielsen, D. M. (2009). Physiological and behavioral differences in sensory processing: A comparison of children with autism spectrum disorder and sensory modulation disorder. Frontiers in Integrative Neuroscience, 3, 29. https://doi.org/10.3389/neuro.07.029.2009