Some children cover their ears in the supermarket. Some gag when certain textures touch their mouths. Some seek constant physical movement or pressure. Some seem almost unresponsive to pain. These responses to sensory experience vary widely across children, and understanding where the line lies between individual variation and a difference that warrants support is genuinely useful.
This guide covers what sensory processing is, how sensory differences present in young children, the range of normal variation, and when assessment and intervention are appropriate.
Healthbooq (healthbooq.com/apps/healthbooq-kids) covers neurodevelopment and developmental differences in children.
What Sensory Processing Is
Every piece of information the brain receives arrives through the sensory systems: sight, hearing, touch, smell, taste, proprioception (awareness of body position), and vestibular sensation (the sense of movement and balance). The nervous system registers this information, integrates it with other signals, and produces a response. Sensory processing refers to this whole chain – from detection to integration to response.
The process is not passive. The nervous system does not simply record all sensory input equally; it filters, prioritises, and modulates. This modulation is partly responsible for individual differences in sensory experience: why one person can focus in a noisy coffee shop and another cannot; why one child is unfazed by rough seams in socks and another finds them intolerable.
A. Jean Ayres, an occupational therapist and neuroscientist at the University of Southern California, developed the theory of sensory integration in the 1960s and 1970s, proposing that difficulties in processing and integrating sensory information contribute to problems in learning and behaviour in children. Her framework has been highly influential in occupational therapy practice, though the evidence base for specific sensory integration interventions continues to be developed and scrutinised.
The Range of Sensory Responses
Over-responsivity (hypersensitivity). A child who over-responds to sensory input perceives ordinary stimuli as more intense, aversive, or overwhelming than most children would. Common presentations include: distress at tags, seams, or certain textures in clothing; gagging at food textures; covering ears in everyday noise levels; extreme distress at unexpected touch; avoidance of messy play; and difficulty in environments with competing sensory inputs (busy classrooms, supermarkets).
Under-responsivity (hyposensitivity). A child who under-responds to sensory input may seem to seek more stimulation or to be less aware of sensation than would be expected. Common presentations include: seeking intense proprioceptive input (crashing into furniture, seeking tight hugs, bearing down heavily when drawing); high pain tolerance; not noticing when their face is dirty; difficulty with self-regulation without physical stimulation.
Sensory seeking. Some children actively seek high-intensity sensory experiences – spinning, jumping, touching everything, seeking tight pressure. This can be a feature of under-responsivity or a separate pattern.
Normal Variation
Lucy Jane Miller at the STAR Institute for Sensory Processing, whose research on the prevalence and impact of sensory processing differences is among the most extensive available, estimates that 1 in 20 children has sensory processing differences significant enough to affect daily functioning. This means the remainder – 19 in 20 – have sensory preferences, quirks, and variations that fall within the typical range.
In young children (under 3 years), some degree of sensory reactivity is developmentally normal. Toddlers can be hypersensitive to foods, textures, and sounds as part of typical sensory development. The neural systems involved in modulation are immature and continuing to develop. Many children whose parents would describe as "very sensory" at age 2 have developed more typical modulation by age 4-5 without any intervention.
When Sensory Differences Warrant Assessment
Sensory differences are worth assessing when they are: significant in intensity; consistent across contexts; and affecting daily functioning in areas such as eating (food texture avoidance severe enough to limit diet to the point of nutritional concern), dressing (unable to wear necessary clothing), sleep (arousal sensitivity preventing settling), social participation, or the child's emotional regulation and wellbeing.
Sensory differences also frequently co-occur with other neurodevelopmental conditions. Research by Simon Baron-Cohen at the University of Cambridge and others has documented that sensory over-responsivity is present in the majority of autistic children, and Lucy Jane Miller's work documents high co-occurrence with ADHD and developmental coordination disorder. Assessment for sensory differences should therefore often be part of a broader developmental assessment rather than isolated.
Paediatric occupational therapists assess sensory processing through structured observation, standardised assessment tools (including the Sensory Profile developed by Winnie Dunn at the University of Kansas), and parent report. Sensory-based OT interventions, including sensory integration therapy, have evidence of benefit for some outcomes, though the research base is mixed and continues to develop.
Key Takeaways
Sensory sensitivity – heightened or reduced responsiveness to sensory input including touch, sound, light, smell, and movement – varies considerably among children. Some degree of sensory variation is normal in early childhood. When sensory responses are extreme, consistent, and significantly affect daily functioning (meals, dressing, sleep, social participation), assessment by a paediatric occupational therapist is appropriate. Sensory differences frequently co-occur with autism spectrum condition, ADHD, and developmental coordination disorder, but can also occur independently. The concept of 'sensory processing disorder' as a standalone diagnosis is not universally accepted by classification systems, but sensory processing differences are clinically real and treatable.
