How My Brain Deceived Me, and Why It’s Okay

When springtime starts approaching in Berlin, I begin to have conflicting feelings. On the one hand, I feel relieved that the long, dark winter is coming to an end. On the other, I’m terrified by my yearly allergy season and the possibility of sneezing myself to death.

A friend informed me that I could undergo desensitization, a medical treatment for environmental allergies that might alleviate my misery.

While I was delighted by the news, I was intimidated by the lengthy procedure. I would need to get five customized shots for five consecutive weeks and repeat the process for three years. Nevertheless, I underwent the necessary allergy test and scheduled the shots. The clinic is 7 km from my place. I pulled my bike out of the storage room and headed out. The route was hilly, hillier than I expected for a flat city like Berlin. I took the first shot and waited for half an hour in the clinic just in case I had an anaphylactic reaction, an acute allergic reaction that, I’ve been told, is not so pleasant. Before I left, the doctor instructed me to watch for unusual symptoms and to contact them immediately if I noticed any.

The next day, my right thumb started hurting, especially under the nail. I rationalized the pain, thinking I might have hurt my finger while pulling my bike out of the storage room, and dismissed it. The pain subsided in two days.

The following week, the same thing happened. I went to the doctor’s clinic, got my shot, waited half an hour, went back home, and then my thumb started hurting again. This time I was certain I hadn’t bumped my thumb anywhere, and the pain occurred after I received the shot. I began to contemplate the odds: what were the chances of this event (my thumb hurting in precisely the same way and place) happening after I got a desensitization shot? Yet, I convinced myself it was just a rare coincidence. After all, I’d sound silly telling my doctor that my right thumb hurt after every shot.

A week later, I received my third shot, but this time, I asked the doctor to administer the injection in my left arm to see if my left thumb would hurt instead of the right one. I didn’t mention the pain to my doctor. However, before leaving the clinic, I casually asked the nurse, “What symptoms might people experience after getting a desensitization shot?” As expected, right thumb pain wasn’t on the list. The next day at home, I felt the same pain in the exact same right thumb, right under my nail! At that point, I was convinced it had to be related to the desensitization, and I resolved to inform my doctor.

During the fourth visit, I mentioned to my doctor, “Every time I receive the injection, my right thumb aches. Is this common?” I noticed her expression shift from confusion to one of mild exasperation. She assured me politely that she had never heard, seen, or read about such a phenomenon. I left the clinic reconciling with the notion that my doctor probably thinks I’m daft.

While cycling back home and going uphill, I became frustrated with my bicycle’s gear shifter; it was just too stiff and hard to adjust. It clearly needed some oil. That’s when it dawned on me: it wasn’t the shot. It was the bike shifter all along.

“Yep, the classic ‘Correlation does not imply causation, again,’” I told myself while wrestling with the stubborn gear shifter.

In the days that followed, I found myself reflecting on why I was so eager to establish a causal story between the shots and my thumb pain. Intellectually, I had hard time convincing myself, but I still asked the doctor in the end.

Our brains are constantly making up stories and making guesses, and that’s okay if we actively work to disprove them instead trying to prove them right or, worse yet, accepting them without any scrutiny.

We always begin with a guess, a conjecture. To move closer to the truth, we must try our best to disprove our guesses. When we fail to do so, we know we are a step closer to the truth. However, we can never be sure we are truly there.