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Hypo- and hyperresponsivity

🌿ExperientialPeer-reviewed

6 min read

Pattern

Autistic people — especially those with co-occurring intellectual disability — frequently respond to sensory stimuli with intensities that diverge from the typical population, in both directions. Hyperresponsivity is an unusually strong response to stimuli that most people find manageable. Hyporesponsivity is an unusually weak or absent response to stimuli that most people notice clearly. Crucially, both patterns can appear in the same person, across different senses, and across different contexts. The pattern is now formally recognised as a diagnostic criterion of autism spectrum disorder (DSM-5, 2013) and is the most-studied sensory processing feature of autism.

Observations

This pattern is supported by peer-reviewed evidence as well as extensive practitioner observation. The observations below integrate both.

  • It is heterogeneous within the individual. One person may be hyperresponsive to sound and hyporesponsive to pain. Another may be hyperresponsive to light but only in specific circumstances (tired, hungry, unwell). There is no single sensory profile of autism.
  • It is context-dependent. A 19-year-old man described in the SGL synthesis is hyperresponsive to auditory input in most environments but can block all sound at a darts match he loves. The same nervous system behaves differently depending on what the person is attending to and how safe they feel. The SGL authors use this example to caution against treating hyperresponsivity as an organic defect detached from environment and motivation.
  • When intellectual disability co-occurs, the pattern shifts. Systematic review evidence (Werkman et al. 2022) finds that hyporesponsiveness and sensory seeking are specifically elevated in autistic people with ID, and that hyporesponsiveness is associated with the poorest behavioural outcomes. This is counter to the intuition that the loud, distressed, obviously-suffering presentation is the most serious — the quiet, disengaged presentation may be worse.
  • Higher cognition does not buffer. Werkman et al. (2020) found that higher cognitive abilities were associated with more emotional and behavioural problems linked to sensory processing differences, not fewer. See Werkman 2020 — Cognitive abilities moderate sensory–behavioural links.
  • Reactions can be delayed. Some people appear fine during a high-input episode and fall apart hours later, when the cognitive resources used to hold it together run out. The delayed reaction is part of the pattern, not a separate event.
  • Absence is data. The SGL synthesis is emphatic on this point and it is why they prefer “responsivity” over “reactivity”: a person who does not flinch at a loud sound is showing you something about their sensory processing. The absence of response is the observation. Do not infer that nothing is being processed.

Hyperresponsivity — typical presentations per sense

  • Auditory. Covers ears, withdraws from busy environments, flinches at unexpected sounds, becomes distressed in echoing spaces, cannot tolerate fluorescent-light hum or fridge motor noise that others do not notice.
  • Visual. Avoids bright light, squints under fluorescents, distressed by flicker, overwhelmed by visually busy environments, cannot read certain colour combinations, fatigues quickly in high-visual-load settings.
  • Tactile. Refuses certain clothing textures, removes tags and seams, avoids being touched lightly (firm pressure may still be welcome), distressed by unexpected physical contact.
  • Olfactory. Gags at perfumes, cleaning products, certain foods cooking; avoids specific rooms; notices smells others do not.
  • Gustatory. Limited diet, extreme reactions to unfamiliar textures or flavours, specific tolerances that do not match calorie or nutritional needs.
  • Vestibular. Distressed by lifts, stairs, being moved unexpectedly; motion sickness; avoidance of playground equipment.
  • Proprioceptive. Uncomfortable with clothing that touches the body at unexpected pressure, distressed by small changes in weight distribution.
  • Interoceptive. Overwhelmed by strong internal signals — hunger, fullness, a full bladder — that others can ignore.

Hyporesponsivity — typical presentations per sense

  • Auditory. Does not orient to name or to sudden sounds; appears “deaf”; parents often ask for hearing tests which come back normal.
  • Visual. Does not notice visual cues that would normally register; misses facial expressions; stares past objects.
  • Tactile. Does not notice light touch; may not react to pain or injury; can seem unaware of clothing disarranged, food on face, skin irritation.
  • Olfactory. Does not notice smells that others find strong; may not notice own bodily smells, spoiled food, or gas.
  • Gustatory. Does not differentiate flavours; may eat food that has gone off.
  • Vestibular. Does not feel dizzy after spinning; can tolerate motion that makes others sick; may not notice loss of balance.
  • Proprioceptive. Does not know own strength; bumps into things; poor body awareness; “clumsy” that is not motor-based.
  • Interoceptive. Does not notice hunger, thirst, fullness, needing the toilet, tiredness, becoming ill until the signal is extreme. Plausibly related to alexithymia and to difficulty identifying one’s own emotions.

The common case is mixed

Most autistic people are not uniformly hyper- or hyporesponsive. They are hyperresponsive to some inputs and hyporesponsive to others, and the map differs between individuals. This is why this wiki emphasises individual [[02-practice/strategies/building-an-individual-prikkelprofiel|prikkelprofielen]] (stimulus profiles) rather than type labels.

Possible mechanisms

The SGL synthesis reviews several competing mechanistic accounts, none yet definitive:

  1. Modulation problems. The brain under- or over-weights incoming stimuli. Proposed by Ornitz & Ritvo (1968), elaborated by Grandin (2006).
  2. Filter dysfunction. The reticular formation, thalamus, cerebral cortex, and insula — the four structures Ben-Sasson et al. (2009) identify as the stimulus filter — are set differently.
  3. Integration problems. Stimuli arrive but do not combine coherently into multi-sensory experience (Hermelin & O’Connor, 1964).
  4. Arousal differences. Atypical physiological arousal shapes what can be processed (Hutt & Hutt, 1964; Rimland, 1964).

These are not mutually exclusive, and the current best reading combines elements of all four. None fully explain the within-person variability, which is why the SGL synthesis is cautious about mechanistic claims.

Practical implications

  • Treat hyporesponsivity as serious. The review evidence consistently links it to the worst outcomes. A quiet, disengaged presentation is not “easy” — it may be the presentation most at risk.
  • Build individual profiles. See Building an individual prikkelprofiel.
  • Aim for stimulus balance, not suppression. See Prikkelbalans — stimulus balance.
  • Adjust environment, not just person. The SGL case of the darts match shows that the same nervous system behaves differently in different contexts. Environmental change is often the most effective intervention.
  • Never interpret absence of response as absence of experience. Response is not the only possible reaction; overwhelm can present as stillness.

Evidence notes

The core pattern (hypo- and hyperresponsivity as heterogeneous, within-person and between-person, and more pronounced in autism with ID) is peer-reviewed and reflected in the DSM-5. The Werkman 2022 review is the strongest systematic evidence for the subtype-specific findings in ID. The Werkman 2020 result on cognitive moderation is based on a single cohort and needs replication.

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