No two brains, not even those belonging to identical twins, are alike. Every single one follows a unique path of development because no two sets of embodied, in-the-world experiences are ever the same. Which is why, in 1998, Australian sociologist Judy Singer coined the word “neurodivergent” to call attention to differences in how brains form.

Singer’s term does, however, beg another, more complicated question: where does a “normal” brain end and an atypical one begin? My own experiences with brain difference began about 11 or 12 years ago when a friend quietly admitted in a Twitter post that an online test for autism showed him to be “within range.” It would be the first and last time he would ever say this. Social awkwardness that included an aversion to hugging, emotional outbursts and an obsession with details others found inconsequential told the rest of the story, but only to those who observed carefully enough.

As hard as it increasingly became to be around him—because the symptoms of autism (or Asperger’s, its milder form) became more pronounced as my friend grew older and because he never sought help for it—there was always a part of me that understood him. He was bright, very bright; just different. Someone who couldn’t fit in. That quirkiness, along with the terrible isolation he suffered (and for which I always felt the profoundest sympathy), were enough to keep me around for a very long time.

It took me many years to understand that friendship and the powerful bond we shared. If he was the irritable child who grew into an even more irritable bear, I was the anxious child who cried all the time and jumped out of her skin whenever someone tried to tickle her. As an adult, I learned to control my emotions, and to a more limited extent, my physical reactions to touch. No one knew what I was thinking and no one, except to the few who got close enough to me, knew my physical sensitivities. My friend was mostly like that, too, though the grouchiness did seem to worsen as he got older.

But my story was more complicated than that. My friend told me he had always been the odd one out. I, however, had had a gift, up until kindergarten, for making friends with children I didn’t know at the local beach. They could be cruel to me; but in the end, they accepted me. My mother told me that after I started school, after things between her and my father ended, I turned inward and dove headlong into books. That sounded about right. Unlike my parents—and especially my mother—they didn’t yell, scream, hit or threaten. They let me alone to breathe and just be.

Introversion followed and stuck because it, like solitude, felt like natural states. What wouldn’t know until I went into therapy as an adult is that the sensitivities that made me crave solitude were perhaps not all inborn; that some can develop in the aftermath of psychological, physical and/or emotional traumas. And that regardless of whether sensitivities are inherent or created by environmental factors, they can be indicative of neurodivergence. The one difference being that where an inherent sensitivity may be genetically wired into the brain, one acquired through trauma can change the brain by changing how it functions.

There was one other thing I wouldn’t know until curiosity pushed me to explore the topic. Eight years years before the lexical emergence of “neurodivergent,” psychologist Elaine A. Aron was starting her now-landmark study on high sensitivity in humans. Her work eventually led her to theorize that 15 to 20% of the population shared the ability to process external and internal stimuli, including sound, light, pain and hunger, at deeper levels than those without that trait. And that the ability itself arose out of a combination of genetic and environmental factors.

I first heard the term Aron used to refer to these individuals around 2016 while talking to a librarian friend. At that point I was at the last college where I would ever teach and being an adjunct had begun to feel overwhelming. I could not understand why; and the librarian heard more than an earful of my rants. One day she offered an insight that initially made me balk. Have you ever thought that maybe you’re an HSP: a highly sensitive person? She grabbed a book from her office shelf and handed it to me. It’s is a real, documented thing. I’m that way myself.

The book, Making Work Work for the Highly Sensitive Person, made me understand everything about her that had seemed peripheral, from the quiet, uncluttered office to the door she sometimes kept closed. What she had was what many HSPs not only prefer but need: a space apart, dedicated alone time and the ability to limit interaction with others. Too much stimulation and like turtles, we duck into our shells. She also did work that allowed her to help others and feel appreciated for her efforts. I loved teaching; but being a disposable cog in the higher education machine had drained the job of meaning.

Labels made me wary. But everything the book said made sense. I wasn’t just shy or someone who preferred my own company; I had a brain that processed the world around me in ways the majority of brains did not. The more reading and research I did, the more everything made sense, including the closeness I had once felt to my Aspergian friend. Like autism, high sensitivity existed on a spectrum that measured levels of intensity associated with emotional and sensory processing issues. Where autism was different—and more complex—was in how it also involved cognitive issues that did not usually affect HSPs.

Later, I took Aron’s HSPScale test and scored 21 out of 27 points, with 14 being the threshold for HSP. The test has been criticized as too general to be accurate; but by that point, the results had broken down the last of my resistance. I wasn’t just the one who secretly cried at sad movies. I was also the one who rarely left the house without sunglasses to filter out the glare that sometimes gave me headaches and a headset to block out street noises that could scrape across my nerves like nails across a chalkboard. It was good to have names—HSP, neurodivergent—to describe a temperament and brain that I knew were different. And to recognize what an old friendship had been trying to tell me about who I really was.