“Mama! What's for dinner?” I ask as I enter the kitchen. The rich aroma of biryani fills the air. “Ahh, so we are eating biryani today,” I say with satisfaction, as my eyes finally fall on the sizzling pot.

And then it strikes me. I smelled the food before I saw it.

Does that mean the sense of smell is stronger than the sense of sight?

On BBC’s Cunk on Life, the host Philomena Cunk, played by comedian Diane Morgan, posed a similar question in one interview. Sitting across from physicist Professor Brian Cox, she began talking about the speed of light with a serious expression.

“So the speed of light is ‘99.999999%’ of its maximum. And light travels at about 299,792 kilometers per second.”

Then came the question: “Your sense of smell is faster, isn’t it?” Cox, momentarily baffled, answered, “No,” managing to keep a straight face.

The moment is clearly meant to be funny. Yet hidden in that joke lies a genuine scientific question. Light is supposedly the fastest thing in the universe. However, in our everyday lives, we often notice a smell before we see its source. Why is that?

This phenomenon is known as olfactory pre-detection, which means that your sense of smell and your sense of sight have completely different mechanisms.

Your sense of sight is highly affected by your line of sight. You see something the moment light rays travel to the retina, which then sends the signal to the brain to process the image. Light rays constantly reach our eyes, since we are almost always looking at something.

The sense of smell, however, depends on tiny particles in the air. Through diffusion, odor molecules travel across a room until they reach the olfactory epithelium in the nose. Hair-like structures called cilia trap these molecules and send signals to the brain for interpretation.

This often triggers memories or emotional reactions. That is why we feel nostalgia when smelling perfume, while unpleasant odors trigger disgust and pleasant ones evoke happiness.

Olfactory pre-detection explains why we can smell an odor before seeing its source: odor molecules may already be present in the air, while our line of sight might be blocked or directed elsewhere.

Consider the biryani example again. I enter the kitchen looking directly at my mother while asking about dinner. Meanwhile, my nose has already detected the spices. This prompts me to glance at the pot hidden behind her.

You might think the smell reached us first—and in a way, it did. But this does not mean our sense of smell is faster than sight. Light remains the fastest mode of transport in the universe. Its detection, however, depends on whether the source is visible or obstructed.

We are constantly looking at our surroundings, but the atmosphere usually remains unchanged. When a new odor enters, the nose immediately detects it because it has been sampling the same air for so long.

It is like eating bland porridge every day—when pancakes with maple syrup suddenly appear, your mouth starts watering instantly.

Researchers at the Chinese Academy of Sciences found that humans can detect the order of two different odors presented just 60 milliseconds apart—faster than the average human blink. This suggests that the olfactory system has temporal sensitivity comparable to vision.

“A sniff of odors is not a long-exposure shot of the chemical environment… it incorporates a temporal sensitivity on par with that for color perception.”

Another example is smoke from a fire. When entering a smoky space, vision can be impaired, but the smell alerts us to danger and prompts immediate action.

While light may travel faster, our sense of smell has its own survival advantages. No matter the shape or size of your nose, sometimes it is all you need to stay safe.

Smelling dinner before seeing it is not a superpower—it is simply the result of how our senses collect information differently. While light outruns everything in the universe, scent molecules often have the advantage of already being present in the air.

Our noses act as constant air monitors, quietly tracking chemical changes until something new—biryani, rain, or smoke—triggers an alert.

That first whiff is the body’s way of saying, “Look around. Something is here.”

So the next time someone jokingly asks, “Why do we smell dinner before we see it?”—send them this article. They may never hear the joke the same way again.

Credits

• BBC. (2022). Cunk on Life [TV series episode]. In Cunk on Earth. Written by Charlie Brooker. BBC Two.
• Zhou, W., Cao, M., Zhang, X., Wei, X., Zheng, Q., & Zhang, X. (2025). Humans perceive odors with similar temporal precision to vision. Neuroscience News.