Sensory under-responsivity is a pattern in which a person’s nervous system registers everyday sensory input more slowly or weakly than expected, leading them to seem unaware of stimuli that most people notice easily. A child who doesn’t flinch when a ball is thrown at their face, an adult who fails to notice food stuck to their cheek, or someone who seems unbothered by a room that is uncomfortably hot for everyone else may all be showing signs of this pattern. Among the various sensory processing differences studied in neuroscience, under-responsivity stands out because it is often the least obvious to outside observers and, in conditions like autism, has turned out to carry some of the strongest links to social difficulties.
What Sensory Under-Responsivity Actually Looks Like
The core feature is a muted or delayed response to sensory input. This can show up in any sensory channel: touch, sound, sight, taste, smell, or the body-awareness senses like proprioception (knowing where your limbs are) and the vestibular system (your sense of balance and movement). Someone who is under-responsive to touch might not notice a tap on the shoulder. Someone under-responsive to vestibular input might not get dizzy on a spinning ride that would leave others nauseated. An under-responsive sense of proprioception can make a person seem clumsy or uncoordinated, bumping into doorframes or gripping objects too hard because the body’s feedback about force and position comes through faintly.
In clinical and research settings, the term often appears alongside related labels like “low registration” and “hypo-responsivity.” These are used almost interchangeably, though “low registration” specifically refers to the tendency to miss sensory events that are within a normal range, while “hypo-responsivity” is the broader umbrella. Research with children on the autism spectrum has consistently found hypo-responsivity emerging as its own distinct factor in sensory assessments, separate from sensory seeking, sensitivity to taste and smell, and movement-related patterns.
How It Differs from Sensory Seeking and Over-Responsivity
Under-responsivity is often confused with sensory seeking, and the two do overlap in some people, but the underlying experience is quite different. A sensory seeker actively craves intense input: they spin, crash into cushions, chew on non-food objects, or blast music because the stimulation feels good or satisfying. An under-responsive person, by contrast, isn’t necessarily craving anything. They just don’t notice that the input is there in the first place. The signal arrives at a whisper rather than a shout. Some individuals are both: they under-register input at lower intensities and then chase stronger sensory experiences to compensate, which is why research has identified an “under-responsive and sensation seeking” profile that clusters together in sensory assessments of autistic individuals.1PubMed Central. Exploring sensory phenotypes in autism spectrum disorder
Over-responsivity sits at the opposite end. Where an under-responsive person barely notices the hum of a fluorescent light, an over-responsive person finds it agonizing. These patterns can coexist in the same person across different senses: someone might be under-responsive to touch but over-responsive to sound. A laboratory study comparing children with autism and children with sensory modulation disorder found that the autism group tended toward lower baseline physiological arousal and more under-responsivity, while the sensory modulation group showed higher reactivity to new stimuli and more sensory seeking behavior.2PubMed Central. Physiological and behavioral differences in sensory processing: a comparison of children with autism spectrum disorder and sensory modulation disorder That distinction matters because it suggests the nervous system’s baseline “volume setting” differs between the two groups, not just their behavioral response.
The Strong Connection to Autism
Sensory under-responsivity has been studied most intensively in autistic individuals, and the link is striking. A meta-analysis pooling data from 14 studies found that the single largest sensory difference between autistic and non-autistic groups was in under-responsivity, even larger than the differences seen in over-responsivity or sensation seeking.3PubMed. A meta-analysis of sensory modulation symptoms in individuals with autism spectrum disorders That finding challenged earlier assumptions that sensory issues in autism were mostly about being overwhelmed by too much input. In reality, failing to register enough input appears to be the more defining pattern.
This doesn’t mean every autistic person is under-responsive. Cluster analyses of sensory profiles in autism have found at least five distinct patterns, ranging from “sensory adaptive” (minimal differences from the general population) to “generalized sensory differences” (difficulties across the board).4PubMed Central. Exploring sensory phenotypes in autism spectrum disorder Under-responsivity is more common and more pronounced in autism as a group, but individual variation is enormous. Some autistic people are highly over-responsive to certain stimuli and under-responsive to others, which can make their sensory experience confusing both to them and to clinicians trying to help.
Why Under-Responsivity Hits Social Functioning Hard
One of the more consequential findings in this area is the link between under-responsivity and social difficulties. Research examining tactile responsiveness in autistic children found that hypo-responsiveness to touch correlated strongly with greater social and communication impairments. Perhaps more surprising, tactile over-responsiveness did not show that same relationship.5PubMed Central. Tactile responsiveness patterns and their association with core features in autism spectrum disorders The implication is that failing to register social touch, a pat on the back, a handshake, the brush of a friend’s arm, may matter more for social connection than being overwhelmed by it.
Broader work on sensory experiences and social functioning reinforces this picture. Children with more intense sensory issues, including under-responsivity, tend to show greater social interaction difficulties and lower overall functioning.6PubMed Central. The relationship between sensory experiences and social functioning in children with autism spectrum disorder Think about it from a practical standpoint: social interaction depends on picking up subtle cues. A friend’s change in tone of voice, a shift in facial expression, the way someone leans toward you or pulls away. If the nervous system is slow to register these signals, the person misses them entirely and seems disconnected or disinterested, even when they aren’t.
This makes under-responsivity a different kind of social barrier than, say, social anxiety. An anxious person detects the social signals but struggles with how to respond. An under-responsive person may not detect them at all. Interventions designed primarily around managing overwhelming sensory input don’t address this gap, which is part of why distinguishing between under- and over-responsivity matters so much for planning support.
What Happens in the Brain and Nervous System
The neuroscience behind under-responsivity is still being pieced together, but some patterns have emerged. The laboratory study mentioned earlier, comparing autistic children with children who had sensory modulation disorder, measured sympathetic nervous system markers during sensory challenges across five different senses. Children with autism showed lower baseline arousal and lower physiological reactivity to stimuli.7PubMed Central. Physiological and behavioral differences in sensory processing: a comparison of children with autism spectrum disorder and sensory modulation disorder In other words, their autonomic nervous system wasn’t revving up in response to new input the way it typically should. This points to the issue being less about what the sense organs detect and more about how the brain processes and amplifies that information.
Research combining brain imaging with EEG has looked at neurochemical signals in areas of the brain involved in integrating sensory information. One study measured levels of a neurotransmitter marker called Glx in the right temporoparietal junction, a brain region involved in integrating input from multiple senses and in social cognition. Higher Glx levels in that region were associated with lower scores on sensory registration, sensitivity, and avoidance measures, particularly in autistic children.8PubMed Central. Associations between sensory processing and electrophysiological and neurochemical measures in children with ASD: an EEG-MRS study This hints at an imbalance between excitatory and inhibitory brain signaling that could make sensory input harder to detect or prioritize.
An interesting nuance is that early-stage sensory processing itself may not be broken. A study examining auditory and visual brain responses in children with sensory processing disorder found that basic sensory registration and early perceptual processing appeared largely typical, not substantially different from typically developing children or from autistic children.9Frontiers in Integrative Neuroscience. Multisensory Audiovisual Processing in Children With a Sensory Processing Disorder (I): Behavioral and Electrophysiological Indices Under Speeded Response Conditions The eyes and ears work fine. The trouble seems to start further downstream, where the brain decides what to pay attention to and how much weight to give different signals. The analogy isn’t a broken microphone; it’s more like a sound engineer who keeps the volume knob turned too low.
Genetics and Early Life Risk Factors
Twin studies have made clear that sensory processing styles are substantially heritable. One large twin study found that sensory reactivity was about 66 to 71 percent heritable, and autistic traits were 62 to 75 percent heritable, with significant genetic overlap between the two.10PubMed. Examining the Association Between Autistic Traits and Atypical Sensory Reactivity: A Twin Study But the different dimensions of sensory processing aren’t all driven by the same genetic influences. A study tracking infants found that sensory seeking, sensitivity, avoidance, and low registration each had their own mix of genetic and environmental contributions, with significant additive genetic effects unique to each dimension.11PubMed Central. Different sensory dimensions in infancy are associated with separable etiological influences and with autistic traits in toddlerhood
For low registration specifically, a co-twin-control study of autistic and non-autistic twins found that the link between autistic traits and low registration was influenced by non-shared environmental factors rather than purely by genetics.12PubMed Central. A co-twin-control study of altered sensory processing in autism That’s a striking distinction from sensory sensitivity, where the link to autistic traits was mostly genetic. It suggests that under-responsivity may be more shaped by individual experiences, including experiences that differ even between identical twins growing up in the same household.
Prematurity is one well-documented environmental risk factor. A systematic review found that preterm birth negatively affects sensory processing, with gestational age, male sex, and white matter brain lesions emerging as risk factors for sensory processing difficulties.13PubMed Central. Sensory processing during childhood in preterm infants: a systematic review Additional work found that the length of time spent in a neonatal intensive care unit was also positively associated with sensory modulation problems, alongside white and grey matter brain abnormalities.14PLOS ONE. Sensory modulation in preterm children: Theoretical perspective and systematic review The NICU environment itself, with its constant alarms, bright lights, and medical procedures, may shape how the developing brain calibrates its responses to sensory input, potentially contributing to either heightened or dampened reactivity later on.
Under-Responsivity Beyond Autism
While most research has focused on autism, under-responsivity appears in other populations too. Adults with ADHD show differences in sensory processing compared to adults without ADHD, including significantly different scores on low registration measures.15PubMed Central. Sensory profiles in adults with and without ADHD The connection between ADHD and sensory processing is getting more research attention, and longitudinal work using brain-based markers of excitatory-inhibitory balance has found links between cortical development and both hyper-responsivity and hypo-responsivity from infancy onward in cohorts enriched for autism and ADHD.16Translational Psychiatry. Cortical markers of excitation/inhibition balance are associated with sensory responsivity from infancy in longitudinal cohorts enriched for autism and ADHD
Under-responsivity also isn’t exclusive to neurodevelopmental conditions. In the general adult population, the low registration sensory style has been linked to patterns of emotional and external eating: people who tend to miss or under-respond to bodily sensory cues were more likely to eat in response to emotions or environmental triggers rather than internal hunger signals.17British Journal of Occupational Therapy. Sensory processing styles and eating behaviors in healthy adults That’s not a disorder; it’s a dimension of normal human variation that has real effects on behavior. Most people sit somewhere on the spectrum from highly sensitive to fairly oblivious across their different senses, and the under-responsive end of that continuum shapes everyday habits in ways people rarely attribute to sensory processing.
Proprioception, Clumsiness, and the Less Obvious Senses
When people think about under-responsivity, they tend to picture the classic five senses. But the internal body senses are where under-responsivity can be most disruptive in daily life and hardest to spot. Proprioception, the sense that tells you where your body parts are without looking, directly affects coordination. Research on proprioceptive tasks in children found that simple non-visual movement tasks predicted performance in more complex skilled activities, though many task features beyond proprioception alone contributed to those outcomes.18PubMed. Use of proprioception in normal and clumsy children A child who is under-responsive to proprioceptive input may press too hard when writing, misjudge how much force to use when hugging someone, or have trouble with tasks like buttoning a shirt where you can’t see what your fingers are doing.
Vestibular under-responsivity is another one that flies under the radar. These children may spin without getting dizzy, love being upside down, or fail to catch themselves when they lose balance because the signal that says “you’re falling” arrives too late or too quietly. In adults, vestibular under-responsivity can look like a general tolerance for motion that others find extreme, or it can manifest as poor balance and spatial orientation when visual cues aren’t available, such as in a dark room.
Interoception, the sense of internal body states like hunger, thirst, temperature, and the need to use the bathroom, is also relevant. Children and adults who are under-responsive to interoceptive signals may not eat until they are extremely hungry, not realize they are overheating until they are ill, or have difficulty with toilet training because they don’t register the urge until it’s urgent. This dimension of under-responsivity is less studied but increasingly recognized as important, especially because interoceptive awareness appears to play a role in emotional regulation: if you can’t feel your body’s stress signals building, you may go from calm to meltdown with no perceived warning.
Approaches to Support and What the Evidence Shows
The most established therapeutic approach for sensory processing difficulties, including under-responsivity, is Ayres Sensory Integration (ASI), a form of occupational therapy that uses structured play-based activities to help the nervous system become better at processing and responding to sensory input. A systematic review examining its effectiveness for autistic individuals found moderate evidence supporting its use.19PubMed. Effectiveness of Ayres Sensory Integration® and Sensory-Based Interventions for People With Autism Spectrum Disorder: A Systematic Review “Moderate” in clinical evidence terms means it’s a step above preliminary but short of the strong, replicated evidence base seen for some other therapies. Still, it’s the best-supported option available specifically targeting sensory processing.
For under-responsivity in particular, therapeutic strategies tend to focus on increasing the intensity and variety of sensory input in a controlled way. An occupational therapist might use heavy work activities (pushing, pulling, carrying weighted objects) to boost proprioceptive input, vibrating tools or textured materials to increase tactile registration, or movement-based activities to stimulate the vestibular system. The goal isn’t to “cure” under-responsivity but to help the nervous system become more efficient at detecting and using the input it receives, and to teach the person strategies for compensating in daily life.
Environmental modifications also matter. For a child who is under-responsive, a quieter, less stimulating classroom isn’t necessarily helpful the way it might be for an over-responsive child. Instead, the environment might benefit from more sensory richness: textured seat cushions, opportunities for movement breaks, strong visual cues to supplement auditory instructions, and fidget tools that keep the sensory system engaged. For adults, workplace adjustments might include standing desks, background music, and tactile tools to prevent the kind of zoning out that under-responsive individuals describe when environments are too bland or monotonous.
When Under-Responsivity Gets Mistaken for Something Else
One of the biggest practical problems with sensory under-responsivity is that it often gets misread. A child who doesn’t respond when their name is called might be evaluated for hearing problems. A child who seems disengaged and passive in the classroom might be labeled as unmotivated or inattentive. An adult who doesn’t react to social cues may be seen as rude or indifferent. In young children, under-responsivity to pain can even raise red flags about emotional wellbeing when the real issue is that the pain signal simply isn’t arriving with normal intensity.
The overlap with ADHD-related inattention is another source of confusion. Both conditions involve missing things in the environment, but for different reasons. In ADHD, the person may detect the sensory signal fine but fail to sustain attention to it. In under-responsivity, the signal itself is weak at the neurological level. The distinction matters for intervention: attention-focused strategies won’t address a sensory registration problem, and sensory strategies won’t fix an executive function issue. Given that ADHD and sensory differences frequently co-occur, teasing apart the contributions of each requires careful assessment.
Another common misconception is that under-responsivity is always a problem. At mild levels, it’s just a personality feature. The person who can sleep through thunderstorms, ignore office noise, eat extremely spicy food without flinching, or remain calm during chaotic situations may simply have a higher sensory threshold. That’s an advantage in plenty of contexts. Under-responsivity becomes clinically relevant when it interferes with safety, social relationships, learning, or daily functioning. The line between “high threshold” and “disorder” is drawn by impact, not by the trait itself.