Sensory Hyposensitivity

Sensory hyposensitivity (also called sensory under-responsivity or hyporeactivity) is a sensory processing difference in which the nervous system requires greater intensity, duration, or frequency of sensory stimulation to detect and respond to environmental inputs. Individuals with hyposensitivity may appear not to notice stimuli that others readily detect — failing to respond to their name being called, not reacting to temperature extremes, seeming unaware of injuries, or appearing oblivious to strong odors. Hyposensitivity is reported in approximately 40–50% of autistic individuals, frequently co-occurring with hypersensitivity in different modalities within the same person — a pattern that underscores the complexity of sensory processing differences in autism and related conditions.

Sensory Modalities Affected

• Proprioceptive hyposensitivity — Reduced awareness of body position and movement in space. Individuals may use excessive force when handling objects, press too hard when writing, bump into furniture or people, or adopt unusual postures. They may seek intense proprioceptive input through heavy lifting, jumping, crashing, or squeezing into tight spaces to compensate for reduced body awareness.
• Vestibular hyposensitivity — Reduced responsiveness to movement and gravitational forces. Individuals may seek intense vestibular stimulation through spinning, swinging, rocking, or hanging upside down without experiencing the dizziness that typically limits such activities. Post-rotary nystagmus (the eye movement reflex after spinning) may be reduced, indicating altered vestibular processing.
• Pain and temperature hyposensitivity — Reduced or absent response to painful stimuli or temperature extremes. This can present significant safety risks, as individuals may sustain burns, injuries, or illness without recognizing symptoms. Some autistic individuals report that they process pain signals with a delay — registering pain minutes or hours after an injury rather than immediately.
• Auditory hyposensitivity — Appearing not to hear sounds at typical volumes, failing to orient to novel sounds, or seeming unresponsive to name-calling despite having normal audiometric hearing. Individuals may increase the volume of music or television to very high levels, or may not be startled by sudden loud sounds.
• Tactile hyposensitivity — Reduced awareness of touch, texture, or pressure on the skin. Individuals may not notice food on their face, may be unaware of clothing that is twisted or uncomfortable in ways that would bother others, and may seek intense tactile input through touching surfaces, mouthing objects (persisting beyond the typical developmental period), or rubbing materials.
• Interoceptive hyposensitivity — Reduced awareness of internal body signals such as hunger, thirst, bladder or bowel fullness, fatigue, temperature regulation, and emotional arousal. Interoceptive hyposensitivity can have significant health implications: individuals may not eat when hungry, may not recognize the need to use the bathroom, and may have difficulty identifying their emotional state (a component of alexithymia).

Neural Mechanisms

• Elevated sensory thresholds — Psychophysical testing reveals that hyposensitive individuals require higher stimulus intensity to achieve detection. This elevated threshold is not due to peripheral receptor dysfunction but reflects central processing differences — the brain requires more input before registering the signal as worthy of conscious processing.
• Reduced neural gain — The gain function describes how the brain amplifies weak sensory signals to make them detectable. In hyposensitivity, neural gain may be reduced, meaning that weak or moderate signals fail to be amplified sufficiently for cortical registration. This contrasts with hypersensitivity, where gain is increased.
• Thalamocortical under-connectivity — While hypersensitivity involves excessive sensory throughput, hyposensitivity may involve insufficient sensory relay from thalamus to cortex. Neuroimaging studies show that under-responsive individuals have reduced structural and functional connectivity in thalamocortical pathways, leading to inadequate transmission of sensory information.
• Arousal system dysfunction — The reticular activating system (RAS) regulates baseline arousal and alertness, influencing the brain's readiness to detect and respond to sensory input. Chronically low arousal — which may result from dysregulation of noradrenergic and dopaminergic systems — reduces the brain's overall responsiveness to incoming stimulation.
• Insular cortex processing — The insular cortex is critical for interoception and for integrating sensory information with emotional and motivational states. Altered insular cortex function may contribute particularly to interoceptive hyposensitivity and the disconnection between sensory input and adaptive behavioral responses.

Sensory Seeking Behavior

Hyposensitivity frequently drives sensory seeking — the active pursuit of intense sensory input to compensate for the under-registration of environmental stimulation:

• Movement seeking — Spinning, jumping, rocking, running, swinging, and climbing provide intense vestibular and proprioceptive input. These behaviors may be misinterpreted as hyperactivity or behavioral problems when they actually represent the nervous system's attempt to achieve adequate sensory registration.
• Deep pressure seeking — Seeking tight hugs, heavy blankets, compression clothing, or crawling under furniture provides proprioceptive input that enhances body awareness and may have calming, regulating effects. Temple Grandin's "squeeze machine" was designed based on this principle.
• Oral sensory seeking — Chewing on non-food objects (clothing, pencils, jewelry), mouthing objects beyond the typical developmental period, and strong preferences for intensely flavored, crunchy, or chewy foods provide oral sensory stimulation.
• Visual and auditory seeking — Fascination with spinning objects, light patterns, or moving visual stimuli; preference for loud music, repetitive sounds, or humming and vocalizing to create self-generated auditory input.

Co-Occurrence with Hypersensitivity

A critical insight from research is that hyposensitivity and hypersensitivity frequently co-occur within the same individual, creating a "mixed" or "variable" sensory profile. An individual may be hypersensitive to auditory input but hyposensitive to proprioceptive input, or may fluctuate between hyper- and hyporesponsiveness within the same modality depending on arousal state, fatigue, stress level, and environmental demands. This co-occurrence pattern, described by Dunn's (1997) model of sensory processing, reflects the interaction between neurological thresholds and behavioral self-regulation strategies rather than a single dimension of sensitivity.

Assessment

• Sensory Profile questionnaires — The Sensory Profile (Dunn, 1999) and Sensory Profile 2 assess "low registration" (high threshold, passive response) and "sensation seeking" (high threshold, active response) quadrants that capture hyposensitivity patterns.
• Behavioral observation — Systematic observation of sensory seeking behaviors, response latencies to sensory stimuli, and the frequency and intensity of stimulation required to elicit orienting or behavioral responses.
• Psychophysical threshold testing — Measurement of detection thresholds across modalities to quantify the degree of under-responsivity relative to normative data.
• Physiological measures — Electrodermal activity in response to sensory stimuli may show dampened or absent orienting responses, reflecting the neurological under-registration of input.

Interventions

• Sensory enrichment — Proactively providing regular, scheduled access to intense sensory input in the individual's under-responsive modalities. This may include movement activities, deep pressure, vibration, strong flavors, or other intense stimuli that meet the nervous system's elevated threshold requirements.
• Sensory diet programs — Individualized activity schedules incorporating alerting sensory activities (cold water, crunchy foods, fast movement) to increase arousal and sensory registration throughout the day, designed in collaboration with occupational therapists.
• Environmental amplification — Increasing the salience of important environmental signals: using visual alerts in addition to auditory ones, providing tactile reminders (vibrating alarms for schedules), and using high-contrast visual materials.
• Interoceptive awareness training — Teaching recognition of internal body signals through mindfulness-based approaches, body scanning, biofeedback, and explicit labeling of physiological states. Programs such as the Interoception Curriculum (Mahler, 2017) provide structured approaches to building interoceptive awareness.
• Safety planning — For individuals with significant pain or temperature hyposensitivity, establishing safety protocols: regular skin checks, water temperature limits, protective equipment for high-risk activities, and teaching explicit rules about when to seek medical attention.