Umwelten

Intellectual disability and the limits of neurodiversity

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Summary

Approximately 30-40% of autistic people also have an intellectual disability. They are the population at the centre of this wiki’s origin story: the Dutch Sensatie van een Goed Leven project focused specifically on sensory processing in autistic people with ID (see Sensory processing in autism and intellectual disability). They are also the population that the neurodiversity paradigm, as it has developed over the past two decades, serves least well.

This is not an accusation. It is an observation about how movements grow. The neurodiversity paradigm was built by articulate, self-advocating autistic adults, many of them writers and academics, who could describe their own experience and demand that it be taken seriously. The epistemic tools they developed (the vocabulary of masking, burnout, meltdown, shutdown; the philosophical frameworks of epistemic justice and the double empathy problem) depend on a capacity to self-report that some people with intellectual disability do not have, or do not have in the forms the movement recognises.

The question this page confronts is not whether the neurodiversity paradigm applies to people with intellectual disability. It does, or it should. The question is what must change in the paradigm, and in the philosophical frameworks that support it, to make that application real rather than notional.

The silence at the centre

Every page in this wiki’s philosophy cluster has a version of the same caveat. The philosophy of experience page notes that phenomenological methods may not access the experience of people who cannot provide verbal testimony. The epistemic justice page acknowledges that its framework depends on the concept of a “knower” who can articulate their experience. The ethics of intervention page recognises that consent frameworks break down for people whose preferences may be difficult to determine. The political philosophy page observes that self-advocacy movements are led by those with the resources to lead.

Each of these caveats is honest. Collectively, they describe a gap that honesty alone does not fill. The most marginalised people in the neurodivergent world, those with profound intellectual disability and the highest support needs, appear in these frameworks as edge cases, as the “but what about…” that follows the main argument. They deserve better than that.

Carlson (2010) traced how intellectual disability has been constructed and marginalised within philosophy itself. Western philosophy has historically defined personhood through rationality, and intellectual disability represents the case that puts this definition under the most pressure. If personhood requires rational capacity, what is the status of someone with profound cognitive disability? The question is not merely academic. It determines legal rights, resource allocation, and whether someone is treated as a person whose experience matters or as a body to be managed.

The phenomenological problem

The philosophy of experience page (see Philosophy of neurodivergent experience) argues that different neurotypes inhabit different umwelten: different perceptual worlds constructed by different nervous systems. This argument applies to people with intellectual disability at least as strongly as it applies to autistic people without ID. An autistic person with profound intellectual disability experiences the world through a nervous system that processes sensation differently, in a body that may also have motor and sensory impairments, with cognitive architecture that shapes perception in ways we understand poorly. Their umwelt is at least as different from the neurotypical norm as any other autistic person’s, and possibly more so.

The problem is epistemic access. Nagel (1974) asked “what is it like to be a bat?” and concluded that subjective experience resists third-person description when the sensory apparatus is sufficiently different. For an autistic person who can write or speak about their experience, the Nagelian gap can be partially bridged by testimony. For someone with profound intellectual disability and no reliable means of symbolic communication, the gap is wider and the usual bridge is not available.

This does not mean their experience is unknowable. It means the routes to knowing require different methods. Behaviour is communication, even when it is not intended as such. A person who consistently withdraws from certain sensory environments is telling you something about their umwelt. A person who seeks deep pressure or rhythmic movement is expressing a sensory need. The challenge is interpretation: reading behaviour as evidence of experience without projecting your own experience onto it.

Stefánsdóttir et al. (2018) argued that self-determination for people with profound intellectual and multiple disabilities (PIMD) should be understood through embodied communication rather than verbal expression. Preferences are expressed through the body: approach and withdrawal, tension and relaxation, engagement and disengagement. These are data about the person’s umwelt, and treating them as such is both more respectful and more empirically grounded than assuming that the absence of verbal report means the absence of preference.

Autonomy reimagined

The standard philosophical account of autonomy is individual: a person decides for themselves, based on their own values and preferences, and acts accordingly. This account has never described human life accurately (we are all interdependent, all shaped by relationships and context), but it breaks down most visibly for people with intellectual disability.

Kittay (2019) offered an alternative grounded in care ethics. Her philosophical work, shaped by decades of caring for her daughter Sesha who has profound intellectual disability, argues that autonomy is not the highest human good. Interdependence is the reality. A life of dependence on others is not a diminished life. The quality of that life depends on the quality of the care, the relationships, and the responsiveness of the people around the person.

This reframes the question. Instead of asking “can this person make autonomous decisions?” (which positions intellectual disability as a failure of autonomy), ask “how can the people around this person be most responsive to what they communicate through their behaviour, their body, their patterns of engagement and withdrawal?” The second question does not require the person to be autonomous in the standard philosophical sense. It requires the people around them to be attentive.

The CRPD’s Article 12 pushed this further at the legal level, mandating a shift from substituted decision-making (a guardian decides for the person) to supported decision-making (the person is supported to make their own decisions to the greatest extent possible). For people with mild or moderate intellectual disability, this shift is practical and overdue. For people with profound ID, the implementation is difficult in practice, and Laragy and Olney (2024) documented that most jurisdictions have been slow to operationalise it. The principle remains important even where its application is incomplete: the default should be to maximise the person’s participation in decisions about their own life, not to assume incompetence.

Capabilities at the limit

The capabilities approach (see The capabilities approach) asks what a person is able to do and to be. Nussbaum (2009) addressed cognitive disability directly and argued that the framework applies even when some capabilities (practical reason, full social participation) may never be achievable in their standard form. The question is not “can this person achieve all ten central capabilities?” but “what can be done to expand the capabilities this person does have?”

For an autistic person with intellectual disability, this might mean: ensuring they can experience pleasure and avoid pain (a sensory processing question), maintaining relationships with people who know and care for them (an attachment question), having access to environments that support rather than overwhelm their nervous system (an environmental design question), and having their preferences recognised and respected even when those preferences are expressed through behaviour rather than language.

The capabilities framework is useful here precisely because it does not require the person to meet a threshold of rationality or self-awareness. It asks what they can do and be, and it asks what barriers prevent them from doing and being more. Applied to sensory processing, the framework aligns well with the concept of the prikkelprofiel: understanding what someone needs to function well, not as a clinical exercise in deficit measurement but as a practical effort to expand their comfort, participation, and quality of life.

Sensory processing and the ID population

This wiki’s roots are in sensory processing research with autistic people who have intellectual disability, and the evidence from that research is directly relevant here.

Sensory processing differences appear to be more pronounced in autistic people with ID than in autistic people without ID. The literature synthesis by van Berckelaer-Onnes, Dijkxhoorn, and Hufen (2018) found higher rates of both hypo- and hyperresponsivity, and Matson et al. (2022) confirmed qualitatively different sensory profiles in the autism-ID population. Behaviours that are sometimes labelled as “challenging” (self-injury, aggression, withdrawal, refusal) are often sensory in origin: the person is responding to an environment that their nervous system cannot tolerate, and their behavioural response is communication, not pathology.

Positive Behaviour Support (see Positive Behaviour Support and sensory needs), at its best, recognises this. It asks what the behaviour communicates, what environmental changes would reduce the need for the behaviour, and how the person’s sensory needs can be met proactively rather than managed reactively. When PBS is practised with genuine attention to the person’s sensory umwelt, it is neurodiversity-affirming in practice if not always in name.

What the paradigm owes

The neurodiversity paradigm claims that neurological variation is a natural part of human biodiversity and that all neurotypes deserve respect. If this claim applies only to neurodivergent people who can advocate for themselves, write blog posts, and participate in online communities, then it is not a universal principle. It is a club with an entrance requirement.

Making the principle real for people with intellectual disability requires several things.

It requires treating behaviour as communication. When an autistic person with ID engages in what is labelled “challenging behaviour,” the first question should not be “how do we stop this?” but “what is this person trying to tell us?” This is the epistemic justice principle applied in practice: the person is a knower, even when their knowledge is expressed through their body rather than their words.

It requires investing in the people around the person. The quality of life of someone with profound intellectual disability depends heavily on the quality of their support. Staff training, continuity of care, person-centred planning, and adequate resourcing are not luxuries. They are the infrastructure that makes the neurodiversity paradigm operational for people who cannot implement it for themselves.

It requires the movement to centre the people it has so far placed at the margins. This is the disability justice principle (see Neurodiversity as political philosophy): leadership of the most impacted. For the neurodiversity movement, that means the people with the highest support needs should not appear only in the “open questions” section.

And it requires philosophical humility. We do not fully know what it is like to have profound intellectual disability. We may never know. This is not a reason to stop trying. It is a reason to try harder, with better methods, more attentive care, and a genuine willingness to let the person’s behaviour teach us about their world.

Open questions

Can the neurodiversity paradigm be reformulated to centre intellectual disability rather than accommodate it? What would such a reformulation look like in practice, not just in theory?

What methods can give us better epistemic access to the experience of people with profound ID? Physiological measures (heart rate variability, cortisol, electrodermal activity) can detect stress responses. Behavioural observation can identify preferences. McNally and Alborz (2025) argued that research design itself needs to change to create epistemic agency for people who use augmentative and alternative communication. None of these is sufficient alone. Together, they may approach something like understanding.

How should the neurodiversity movement handle the political tension between celebrating autistic identity (which centres articulate self-advocates) and demanding support for people with high needs (which centres carers, families, and service systems)? These are not opposed goals, but the political structures of advocacy often treat them as though they are.

Key sources

  • Carlson, L. (2010). The Faces of Intellectual Disability: Philosophical Reflections. Bloomington: Indiana University Press.
  • Kittay, E.F. (2019). Learning from My Daughter: The Value and Care of Disabled Minds. Beacon Press.
  • Kittay, E.F. and Carlson, L. (Eds.). (2010). Cognitive Disability and Its Challenge to Moral Philosophy. Wiley-Blackwell.
  • Matson, J.L., Matheis, M., Burns, C.O., Esposito, G., Venuti, P., Pisula, E., Misiak, A., Kaluzynska, A., Kozlowski, A.M. and Sipes, M. (2022). The impact of the presence of intellectual disabilities on sensory processing and behavioral outcomes among individuals with autism spectrum disorders: a systematic review. Review Journal of Autism and Developmental Disorders, 9, 301-316. doi: 10.1007/s40489-022-00301-1
  • McNally, A. and Alborz, A. (2025). Missing methods and epistemic injustice: a scoping review of qualitative research with AAC users. Disability & Society, 40(2). doi: 10.1080/09687599.2025.2458005
  • Nussbaum, M.C. (2009). The capabilities of people with cognitive disabilities. Metaphilosophy, 40(3/4), 331-351. doi: 10.1111/j.1467-9973.2009.01606.x
  • StefĂĄnsdĂłttir, G., Bjornsdottir, K. and Stefansdottir, A. (2018). Self-determination: what can we learn from persons with profound intellectual and multiple disabilities? Scandinavian Journal of Disability Research, 20(1), 29-41. doi: 10.16993/sjdr.830
  • Laragy, C. and Olney, S. (2024). Delivering decision making support to people with cognitive disability: what more has been learned from pilot programmes? Australian Journal of Social Issues, 59(1), 6-23. doi: 10.1002/ajs4.295
  • van Berckelaer-Onnes, I.A., Dijkxhoorn, Y.M. and Hufen, M.A. (2018). Sensory processing in people with autism spectrum disorder and intellectual disability: a literature synthesis. Review Journal of Autism and Developmental Disorders, 5, 58-72.

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