The Problem with “Mental Age”

One unfortunate way that you’ll often see people with developmental disabilities, including autistic people, described is with the concept of mental age. “Oh, they’re a ten year old in the body of a twenty-one year old.” “My daughter’s eleven, but functions as a six year old.” “My cousin’s legally an adult but is mentally four.” This sort of language is used by both professionals and non-professionals alike, and sometimes these sorts of “mental age” assessments are used to make determinations about what sorts of accommodations a person needs or what they will be like to work or interact with.

The problem is that no matter who is using them, the entire idea of “mental age” is not a very accurate, or ultimately useful, way of describing autistic and other developmentally disabled people, not to mention the fact that it is ridiculously infantilizing and therefore promotes a lot of ableism directed towards us. It grates on me any time I hear anyone start to talk seriously about “mental age,” but this practice is so common that I must address it. It’s gotten so bad in some situations that I recently heard a story about a mother’s experience with a “special needs” specializing dentist that refused to schedule her autistic child for an appointment until she gave them an exact-number “mental age” that their child was.

So let’s go through and address some of the many problems with this approach, specifically in regards to autism. If you’re confused as to why this is so inaccurate and problematic, then I suggest you read on. If you’ve found yourself frustrated with this in your own life then hopefully this article can serve as a quick resource you can link back to if you ever need it.

A multi-colored brain diagram has “Mental Age?” written on it in black text.

The entire “mental age” paradigm is largely based on developmental milestones based on observations about the usual developmental schedule for a neurotypical person. People are supposed to have XYZ skills at a certain age and be able to do this or that by a certain age, and so if a person can’t do it by that age then they must actually be developmentally or mentally a younger age. To explain the flaw in this line of thinking, I’ll quote one of my favorite autistic advocates Emma Zurcher-Long: “Autism is not a developmental delay, rather it is a different road entirely.” Autistic people rarely have the smooth even developmental profile of neurotypical people, and so neurotypical developmental roadmaps and timelines cannot be applied to autistic people and be expected to yield accurate information. Just because an autistic person is at a specific developmental mark in one area does not mean that all of their skills/abilities are at that same point as you would expect from a neurotypical person who is at that same spot in that one area. Such spiky developmental profiles among autistic people means that just because an autistic person is “delayed” by neurotypical standards in one area does not mean that they are equally “delayed” everywhere else; indeed, it is entirely possible that they have skills/abilities that are lightyears ahead of what you would expect from a neurotypical person of their same age.

Ultimately, this is essentially the same fallacy that is one of the reasons why functioning labels don’t make any sense. This idea that you can sum up the entirety of a person’s “functioning” with just one descriptive word, or in the case of “mental age,” just one single number. The real world simply does not work that way, because reality is far more nuanced than just a single label or number. For this reason, “mental age” isn’t a very practical way of learning about a person’s needs either. Working with a developmentally disabled twelve year old is not like working with a neurotypical six year old, or five year old, or four year old, or what have you. It’s like working with a developmentally disabled twelve year old. You can’t just treat a person as if they were younger and assume that means you’re suddenly meeting their needs. You also can’t assume that a person’s level of understanding or agency will be equivalent to that of some arbitrary “mental age” or “developmental age” you were previously given.

I’ve heard it said that “autistic toddlers are like neurotypical infants, autistic children are like neurotypical toddlers, autistic teens are like neurotypical children, and autistic adults are like neurotypical teens.” Some people even pull a number out of thin air, confidently proclaiming that “autistic people are about seven years behind their peers, mentally speaking.” And, if you’ll excuse the language, this is quite frankly all complete bullshit. It’s not based on reality or any piece of evidence. Autism is not “this person is magically younger.” It is a symptom of people’s need to compartmentalize autistic people into neat little boxes so that they don’t have to do the extra work to try to understand autistic people on anything more than a very superficial level (though I truly thank those who have put in the extra work to come to a real understanding of autism and autistic people). Just because a person meets the “milestone” for a specific age on a neurotypical developmental timeline does not mean that they are really actually that age mentally, but just stuck in an older body. Us autistic adults are not children in adult bodies. We do not have the minds of children/toddlers. I am not twelve, I am nineteen. A twenty-five year old has the life experiences of a twenty-five year old and twenty-five years worth of memories. Therefore, no matter their developmental profile at that minute they deserve to be treated and described as a fully-fledged twenty-five year old, with accommodations being made for their specific needs of course.

So, that is a very oversimplified version of why “mental age” does not make sense either practically or intellectually. But there’s more to the story here. The infantilization invited by the usage of “mental age” also makes this an ethical issue, as I truly believe that the usage of “mental age” to describe people as being younger than they actually are is incredibly damaging to autistic people.

Infantilism in this specific context is a form of ableism in which disabled people are viewed as an treated as if they were younger than they actually are. As should be obvious, “mental age” and “developmental age” are explicit invitations for infantilization. Infantilism is perhaps the one of the most common forms of ableism experienced by autistic people, and it is so prevalent that many non-autistic people engage in it without even realizing it.

It’s incredibly frustrating when we encounter it. As autistic adults, we’re tired of the infantilization. We’re tired of being talked down to by other adults, or talked to with slow high-pitched sing-songy voices and oversimplified words. We’re tired of being left out of important decisions that directly affect our lives. We’re tired of not being told important information that may impact us. We’re tired of people talking past us, talking about us, to other people in the room while ignoring us. We’re tired of people dismissing our concerns without a second thought. Believe it or not, autistic adults are frequently interested in partaking in adult activities, such as sex, alcohol, and consuming media with mature themes. We’re tired of people trying to censor these things from us as if we were small children.

Two people sit on a couch in a white room. The person on the left condescendingly touches the face of the person on the right, who looks tense and irritated at being infantilized via such a gesture. Image labeled for fair use.

Infantilization is not just frustrating, but it can also be dangerous if people are not given all the information they need to make informed choices, are kept out of the loop about important events, or are never educated on topics that are considered “adult.” Describing someone as being mentally younger than they actually are is blatantly infantilizing and both invites and normalizes this type of ableism for all autistic people. Please, never describe anyone as being any age other than their actual age. It’s bad enough that the masses tend to view autism as something that happens only to small children (and therefore see all autistic people as small children), this sort of fallacy does not need validation.

You might be wondering then what you should do to communicate the needs of an autistic person in your life (or yourself) without using mental age, especially if you’ve relied in the past on this sort of assessment. My answer is that you should do the exact same thing you would do instead of using functioning labels: describe a person’s individual needs, strengths, and challenges when applicable. Instead of saying “this is my 18-year-old daughter who functions as a five-year-old,” say “this is my 18-year-old daughter, who communicates with an AAC app on an iPad and needs support regulating her senses in busy environments.” This is a much more accurate, much more specific, and much more helpful way to communicate about someone’s needs without being infantilizing.

I know that I’m essentially asking you to do more work and put more thought into describing autistic people. But this little bit of extra effort can go a long way in promoting the better treatment of autistic people. We can all play apart in combatting ableism and promoting a world in which autistic people are no longer disabled by the prejudices of society.