Scentsing Reality

I had my first colorblindness test in seventh grade. Well, it wasn’t really a formal colorblindness test so much as a side effect of a science class in which we were discussing vision.

“Look at the picture in your textbook,” the teacher requested. “What number do you see?”

“17,” we answered in near-unison.

“No…” started one boy hesitantly. “It’s a two.”

You can imagine what happened next. As middle schoolers are all too wont to do, we each turned simultaneously to stare at him, our mouths agape. After further clarification that he really did see a 2 despite trying his hardest to see the 17, our teacher confirmed what we already suspected.

“Erik, I think you’re colorblind.”

He looked as if he were about to cry, and I can imagine why. He had just discovered (in front of all his peers, no less) that he was markedly different—that there was something wrong. Something wrong with him. But in reality, nothing was wrong with him, per se. Most likely, a gene on the X chromosome of his ancestral line had mutated decades ago and had been passed down through generations until it manifested itself in him as anomalous trichromacy, a mild color-blindness disorder that primarily affects males. But despite the innocuous nature of color blindness, it has serious implications for his perception of reality. After all, he saw an image that nobody else in that room could perceive. And what is reality, really, if not our perception of sensory information?

On Wednesday night, Dr. Richard Axel of Columbia University began a talk, part of a lecture series presented by the Columbia University Mind Brain Behavior Initiative and sponsored by the Dana Foundation, by arguing just that. He opened with an idea that is, at first, a hard pill to swallow. “Your reality does not exist outside of your brain.” It may seem simple on the surface, but thinking deeply about this question makes me very uncomfortable. How is my world different from everyone else’s? What am I incapable of perceiving? What am I perceiving incorrectly? Am I living a lie?! (OK, perhaps a bit dramatic.)

Axel explained that information from our environment enters our brain through our five senses. Our brain synthesizes this information to create a reflection of the outside world—this synthesis is our reality. And if our brain is constructed based on instructions issued by our genes, then it follows that we are trapped in terms of the type of reality we can perceive. We don’t choose our genes, and because of genetics, Erik could perceive something I could not and vice-versa. Pythons, Axel pointed out, have an extra sensory system—infrared—that allows them to perceive things in the environment that we cannot.

Axel studies one particular sense, olfaction, to attempt to address the question of how the brain uses sensory information to form our subjective realities. Humans sense odors through olfactory receptors located in our noses, just below the spot where a pair of sunglasses would sit. We have approximately 400 functional genes that encode around 1,000 different types of olfactory receptors (note that 1,000 represents the number of variations of receptors; we have approximately five million receptors in total). And here’s the thing: Those 1,000 types of receptors are identical from person to person. We all have the same receptors that are stimulated by the same odors with the same molecular structures. Furthermore, those odors activate certain parts of the brain in exactly the same way from person to person.

So why can one person hate one smell while another loves it? Take, for example, vanillin. Vanillin is a phenolic aldehyde that is composed of eight carbon atoms, eight hydrogen atoms, and three oxygen atoms, but it is more commonly recognized as a smell of scented candles or the flavor of vanilla ice cream. Its structure is easily recognized and therefore easily quantifiable. When I smell vanillin, it activates my olfactory system in precisely the same way that it activates yours. I love the smell, but I know people who can’t stand it.

Axel said he will spend the rest of his life trying to find out how the brain blurs and distorts objective sensory input (like the shape of an odor molecule) into a subjective sensory experience (“Whoa, that smells terrible.”). Unfortunately he had no answers for us at last night’s lecture, but some interesting questions lingered. While loving one smell and hating another might seem bland, there are other aspects of our environment to consider—what sensory abilities do we lack? Why can animals sense an oncoming natural catastrophe? What is there that we can’t see? How different is my reality from yours?

On the other hand, you can simply ignore these questions and continue living comfortably. After all, it’s your world—I just live in it.

–Caitlin Schneider

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One Response to Scentsing Reality

  1. Gerard says:

    This is why I love neuroscience! Unraveling the foundations of our reality!

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