Thanks to Brilliant for supporting this SciShow video! As a SciShow viewer, you can keep building your STEM skills with a 30 day free trial and 20% off an annual premium subscription at Brilliant.org/SciShow. We all have that one friend who spends a little too long pumping gas, taking in all that wonderful, gasoline smell. But unlike the smell of a freshly baked pie or a newborn baby, gasoline doesn’t seem like one of those smells that we should like. After all, we don’t get nutrients from it, we don’t need to look after it, and in a big enough dose, gasoline can make us really sick. But it turns out there are psychological and chemical reasons why so many people love a waft of this gas-station perfume.
Gasoline is made mostly of hydrocarbon molecules, as well as additives that help the car run smoothly. One of those molecules is benzene, which gives gas its distinctive smell. But we don’t really know an evolutionary reason to like this random molecule in gasoline. So it might come down to odor hedonics, which is a science-y way of saying “we like what we like.” We tend to like familiar smells and those that we’ve formed a positive association with in the past. So we might have caught a whiff of benzene while doing something fun like going on a road trip as kids or getting candy from the convenience store. Then we linked those smells and emotions in our minds.
And it’s easier to link emotions to smells than other senses because the brain cells that let us smell things send information to a specialized smell center in the brain before linking directly to the emotion part of the brain called the amygdala. This pathway is different from our other senses that have to go through a less specialized intermediate part of the brain before they’re sent to the amygdala. So that connection between emotion and smell is stronger than, say, taste. Plus, our brain chemistry encourages the association. Benzene causes our brains to release more of the feel-good chemical, dopamine, which makes us feel a bit euphoric.
But like many things that trigger dopamine release, too much of a good thing can be bad. Inhaling too much benzene can break our DNA, which causes cells to die. And depending on which cells die, that can mean a weakened immune system, reproductive problems, or even cancer if you whiff enough of it. So that’s a bit terrifying. But the good news is: if you’re not a professional pumper or around gasoline a lot, the amount of benzene you’re exposed to shouldn’t affect you. Still, it may be best to keep the time at the pump to a minimum.
And if you don’t like the smell of gas, maybe it’s not entirely benzene’s fault. Because, well, there are a bunch of other components of gasoline that don’t smell so great. Things like long chain amines have a fishy or rotten smell, and some people say that long chain carboxylic acids smell like goats. Which might explain why gasoline isn’t appealing to all of us. So there are legitimate reasons why you might love or hate the smell of gas. But whatever camp you fall in, I’m sure we can all agree that the smell of freshly-baked chocolate chip cookies is much, much better.
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