“Humans have five sense: taste, touch, smell, sight, and hearing.” Everybody *knows* that. At least, that’s what we’re all taught in Kindergarten or sometime around then. The only problem here? The “five human senses” are complete bogus. Ok, maybe that’s an overreaction, but it is, at the very least, a gross oversimplification of the actual variety of human senses.
You see, depending on who you ask and how exactly a “sense” is being defined, humans have as many as twenty-six separate senses. This tends to be very surprising to some people, and in this post I’d like to explore more of what these “hidden senses” are, and of course because this is an autism blog we’ll discuss how each of these senses may impact autistic people who process sensory input in unusual ways.
One key part of autism is differences in sensory processing and perception. Some people might even argue that that’s what autism is at its core, a sensory processing and integration differences, and that everything else we associate with autism is just a secondary reflection of this. I won’t be discussing the validity of this hypothesis in this post, because I think we can all agree that sensory processing differences are big in the lives of autistic people, and that’s the point I want to make. Because of our different brain wiring, autistic people have trouble regulating our sensory input and so we very often are either getting too much of or not getting enough of a particular input, and because the brain has to be calibrated and regulated based on the right amounts of sensory input, this can potentially cause many challenges.
Everyone has a sensory profile built around how much of what input they need to give their brain to optimally function, but because autistic people integrate and process senses differently, the sensory profile for many autistic people is just completely off the rails. Many autistic people are therefore either sensory seeking, that is requiring more of a particular input than is standard across the human population, or sensory avoidant, that is requiring less of a particular input than is standard. It’s important to realize that most autistic people are not across the board one or the other, as different sensory systems will be tuned differently, and so an autistic person may be avoidant of one sense but seeking of another. Actually, this is even true within the same sense. It’s very common for an autistic person to, say, find sudden loud noises very painful and find even a few people talking in a group incredibly overwhelming and panic-inducing but also crave playing loud music through headphones. Or an autistic person may not be able to tolerate the bright lights in a supermarket but also like to stare into strobing lights. I know it seems paradoxical if you’re not autistic, but I promise you its not (and going into all the nuances of why is another post all together, and one I’ve already partly covered several times). It’s also possible for a sense to be totally within the standard range for an autistic person. Also, just as every non-autistic person has a different sensory profile, every autistic person has a separate sensory profile, and these may be wildly different between people.
So, now that all that’s out of the way, let’s get on with the senses!
Sight, Hearing, and Smell
I’m starting with these because they’re actually the ones that the “five senses” idea, from my understanding, gets pretty well correct. This category could also include taste because taste and smell are very closely linked. Hearing is probably the most recognizable sensory-different trait in autistics, probably because in general we live in a very loud society, hearing is very hard to escape from, and many autistic people struggle incredibly with this. I’ve actually already written a blog post specifically about auditory sensitivities in autistics, and you can read it by clicking here. Sight is relatively straight forward, autistic people may be overwhelmed by the intensity or type of lighting (a lot of autistics find fluorescent lights to be physically painful or very uncomfortable) or may be overwhelmed when receiving too much visual information, such as from a cluttered or very colorful room. Of course, autistic people may seek visual input too. Smell is similar here too, an autistic person may be overwhelmed by smells that most people don’t even notice, such as cologne or body odor of people passing by, and an autistic person may crave smell as an input and self-stim by smelling things. Without realizing it, I will often smell a piece of food before I put it in my mouth. I’ve been doing this my whole life. This is, at least I think, because I am usually (but not always) under-sensitive to smell and so perhaps its a way of priming my brain with input before eating something.
Even though “touch” is commonly thought of and listed as a single sense, what we call tough is actually at least a half-dozen different senses. Firstly, on a neurobiological level light touch and deep touch are completely different senses. Light touch and deep touch are each sensed via different types of receptors and are each processed completely differently and separately in the brain. For all intents and purposes, they are totally different. Thus, it’s very common for an autistic person to process each differently, and may be generally over-sensitive to one and under-sensitive to the other. The perception of hot and cold on the skin, also generally lumped under touch, is also a completely different sense, which is initiated by thermoreceptors and is also processed completely differently and separately from other senses. The sensation of pain also has its own receptors and is biologically its own sense, and many autistic people are indeed either over or under sensitive to pain which may come across as either unusually high or unusually low tolerance for pain. At its most extreme I’ve heard stories of autistic people who have snapped limb bones in half and didn’t realize it until they had physical problems moving because it simply didn’t hurt that bad, as they were under-sensitive to pain.
Ah, now we’re getting onto senses you may not have heard of! The vestibular sense is the sense of vestibular motion. Inside of your middle ear there are little fluid-filled canals lined with little hairs called cilia. When you head moves the fluid inside these canals flows and moves these cilia, which send information that the brain can interpret as how the body is moving. It also helps inform your sense of balance. This is of course its own sense, and is as such one that autistic people can be over-sensitive to or under-sensitive to. An autistic person that is under-sensitive to vestibular input may crave body movements like jumping, pacing, rolling, etc. Rocking back and forth, a stereotypical and “classic” autistic stim, is a way of stimulating the vestibular sense. Autistics who are undersenstitive to vestibular input may also really love rollercoaster (or not, depending on other factors). An autistic person who is over-sensitive to vestibular motion may seem unsure of themselves when moving quickly, get easily “seasick,” or just generally have trouble with riding in a vehicle like a car or airplane. Over and under sensitivity to vestibular motion could also potentially impair balance.
Proprioception is essentially the sense of “where is my body in space.” From what I understand it relies on detecting which of your muscles are contracted and which are not, which the brain can then interpret to figure out where any particular body part is in relation to the rest of your body. It’s been suggested that differences in proprioception is what causes many autistic people to have trouble with various motor skills or have trouble controlling their body movements, though I don’t think it’s been fully determined whether this is the case or not. Regardless, people who process their proprioceptive sense differently may appear “clumsy” or move in a way that might be perceived as awkward.
To be fair, in order to get a number as high as twenty-six separate senses, you have to include a lot of subconscious senses your body has to maintain homeostasis, such as chemoreceptors that detect the levels of oxygen and other gasses in your blood so that your brain knows when to increase and decrease your breathing rate. Senses such as these, that monitor your internal body state, are classed under the category of interoception. While many of them are not things anybody would notice on a daily basis, there are interoceptive senses that we do notice and effect us in a variety of ways. Some interoceptive senses you feel include things like how hungry or thirsty you are, how hot or cold you are, and whether or not you need to use the bathroom. For example, my sense of hunger is not consistent, and so it’s possible for me to go days without eating simply because I don’t feel hungry. I’ve never actually gone days without eating because someone always reminds me to, but my interoceptive sense of hunger is often so out of whack that’s a distinct possibility.
Technically speaking, emotions are sensory (and they technically fall under interoception). You feel emotions because chemicals stimulate receptors in your brain, which sends signals that then travel down sensory pathways. Therefore, just as autistic people may process other sensory input differently, we also process emotional input differently. We also often become overwhelmed by our emotions in the same way we become overwhelmed by our other senses.
This is a category of “senses” that aren’t tied to a specific sensory receptor, but are things that people still perceive. A major example would be changes in air pressure. Some autistic people find changes in air pressure very difficult to cope with, and as such may have trouble on planes or when the weather changes quickly. I haven’t been able to pin down a great explanation of exactly why this is (my guess would be its a combination of other senses playing together) but ultimately all that’s important is that its known and recognized that this can be a factor. Also in this category would be “chronoception,” or the sense of passing time. This is very difficult to quantify, though apparently some anecdotal reports and evidence suggests that autistic people perceive the passage of time differently, as do people with other neurodivergences such as ADHD.
So, there’s a general rundown of some of the senses, and hopefully some you hadn’t heard of or seriously considered before. Any of these senses could probably have its own article written about it, so if there’s anything you think might be interesting to have elaborated on let me know in the comments and I might do some more focused research and write up an article on the topic!