This is an image of age theory from an early 20th century eugenics textbook.

Mental Age Theory Hurts People with Intellectual Disabilities

Have you ever heard the phrase “that person has the mind of a five year old In an adult body?” It is something many adults with intellectual disabilities, like me, have to deal with. For years, medical professionals have told parents of newly diagnosed Intellectually disabled people that they would mentally be children for their entire lives. Even through I am a 28-year-old, pregnant, married adult, as well as a faculty member at University of Washington, people still tell me that I think like a child. These words are not just offensive language. They can also take away our rights to normal adult lives.  Historically, so-called “mental age theory” has stripped people with intellectual and developmental disabilities of our dignity, our reproductive freedom and our parental rights. Age theory has also been used to strip us of the rights to make adult choices, such as buying alcohol and tobacco or having sexual relationships.

“Mental age theory” was a major feature of the eugenics movement. In many ways, it was also the forerunner of modern-day functioning labels. At the turn of the 20th century, intellectual disability was called “feeblemindedness” and was separated into categories: A moron was somebody who had the mental age of a 9-12 years old, an imbecile was  someone with the mental age of a 6-8 year old, and an idiot was some with the mental age or a 2-5 year old. In Buck v. Bell, a case that legalized forced sterilization of disabled adults, Chief Justice Oliver Wendell Holmes remarked, “three generations of imbeciles is enough” as justification for forced sterilization of people with intellectual disabilities. It was also used to deny us of our freedom and force us to live in institutions.

I work for the University of Washington’s LEND, which is leadership interdisciplinary training for medical professionals. Sometimes medical professionals I work with forget history. I sometimes have to remind them that it is very harmful to use mental age theory when speaking with new parents. Mental age theory discourages parents from teaching their disabled offspring their rights to independence and autonomy.

A lot of my friends with intellectual disabilities have been mislead by mental age theory. They  feel they will never gain independence or get married because they have been told they are children and treated like children for their entire lives. This is why I advocate for people to not use mental age theory at all. We need to tell media they shouldn’t use it to describe disabled adults who are lost or wandering. We need to educate medical professionals that there are better and more respectful way to explain the needs of people with Intellectual/developmental disabilities. Difficulty doing specific tasks isn’t the same thing as being an actual child.

We also need to stop thinking that just because a person likes things that are considered childish, that person is still an adult with the same needs and desires as other adults. I love my little wookies, but I am still an adult. I know many adults without disabilities that enjoy child-like things like cartoons or toys. People with Intellectual and developmental disabilities are treated differently for liking the same things. It’s funny when I meet with non disabled people and they geek out over my little plushy wookies I carry as comfort items. It shows me that adults can enjoy things that children enjoy without people assuming that they are mental children. Please consider this when you hear phrases like “the mind of a five year old” used to talk about adults. Educate people that it is not accurate or appropriate to refer someone with intellectual and developmental disabilities as mentally younger then they are! I not mentally 12. I am mentally 28. I just have an intellectual disability.

23 thoughts on “Mental Age Theory Hurts People with Intellectual Disabilities”

  1. Thank you, Ivanova. I am a psychology LEND trainee, and reading about your perspective and experience with mental age theory was really helpful!

  2. Your comment regarding “childish things” put me in mind of this quote from C.S. Lewis:

    “Critics who treat ‘adult’ as a term of approval, instead of as a merely descriptive term, cannot be adult themselves. To be concerned about being grown up, to admire the grown up because it is grown up, to blush at the suspicion of being childish; these things are the marks of childhood and adolescence. And in childhood and adolescence they are, in moderation, healthy symptoms. Young things ought to want to grow. But to carry on into middle life or even into early manhood this concern about being adult is a mark of really arrested development. When I was ten, I read fairy tales in secret and would have been ashamed if I had been found doing so. Now that I am fifty I read them openly. When I became a man I put away childish things, including the fear of childishness and the desire to be very grown up.”

  3. Great article Ivanova! I agree! Mental age and all labels do not help people understand the true capabilities of an individual and result in denial of equal rights and limitations on equity of opportunity.

  4. I remember these categories when I started college. Little did I know that I would end up teaching Special Ed. classes for 29 years. I was continually amazed by these students’ abilities when given a chance. Lables restrict people. They do nothing to help them grow to their fullest potential.

  5. Thank you so much for this article. As the mom of a child with Down Syndrome, this was what I’ve been wanting to hear. Now to educate the medical and school professionals, and the general population. Time to see the whole person, and not use labels to make assumptions, or create limitations.

  6. A 24-year-old person has the body of a 24-year-old, the mind of a 24-year-old, the emotions of a 24-year-old, and the [whatever] of a 24-year-old. *By definition.*

    You know who has the [whatever] of a 2-year-old? A 2-year-old. *By definition.*

    When I was 24, I was different than you were at 24, and we were each different from Laura Ivanova Smith. All three of us were different from your son at 24. People differ.

    And we can say all of that without being rude to anyone.

  7. I going to share some examples people can to explain their love one support needs that don’t use mental age theory. I some people being asking me for alternatives.

    Ivanova needs help with cooking they have sensory issue and may not be able to tell how hot temperatures on starve are. They have someone do the cooking for them.

    Ivanova can’t drive due to developmental disability that cause they to have struggles with multitasking and hand eye cordination.

    Ivan needs help acrossinf busy streets because they don’t understand traffic very will and need support to be safe.

    Ivan may need support with emotional regulation because they process emotions differently then other people.

    There many ways to explain mental age theory without using mental age!

    Please try out these alternatives!

  8. I have a question… I have an 8 yr old son, who is developmentally delayed. I think as he gets older this will have less impact, as he does continue to grow and develop, just slower than his peers. But what this means is that he is often not emotionally ready for the same thing his peers are, and I often try to explain to his school teachers, that his emotional maturity is more like that of a 4 -5 yr old. I come to that conclusion by reviewing developmental milestones that are offered for children. Should I not do this? I wouldn’t do this if he were an adult, but as a child I feel it is important to let some people know that he isn’t ready for something, YET. He is also large for his age, which tends to let people think he is far older than he even is. But I am interested in others perspective on this, other than my own.

    1. Hello Donna, that is interesting situation. I think that reminds of how malnourishment affected my development in first years of life. I was born with developmental delays and when I was adoption I size of younger age. I think it important to be specific to motor function and not on the age. I see age something gain in experience and not development development is how fast or slow body grows function and not really have to deal how long person been born. I can say I developed slowly I did not learn to speak till five and half. My learning was slowed but that don’t change fact I have 28 years of experience. When I was five I was not mentally younger but my body developed at slower rate then those around me. That don’t effect time. I still lived on this earth for sudden amount of time that affect how old I am.

      example. John body grows at slower rate this may affect memory and learning. He may learn in different way.

      I hope that was helpful.

      Ivanova Smith

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