Why Do We Yawn? The Science Says It’s Probably Not About Oxygen

You’ve probably yawned at least once while reading that headline. Yawning is one of the most ordinary things a body does, yet scientists still argue about why we do it. Ask most people and they’ll say it’s to get more oxygen when we’re tired.

Told straight: that explanation doesn’t hold up well. The theory with the most experimental support right now is that a yawn helps cool your brain. Here’s what the research actually shows, and what’s still guesswork.

The oxygen myth

The “we yawn to get more oxygen” idea feels logical. A big gulp of air, a tired brain, job done. But when researchers tested it, it didn’t fit. In 1987, psychologist Robert Provine and colleagues had volunteers breathe air with extra carbon dioxide (3 to 5%) or pure oxygen, and also had them exercise. Their paper’s title sums up the result: “Yawning: No effect of 3–5% CO2, 100% O2, and exercise” (Provine, Tate & Geldmacher, 1987, Behavioral and Neural Biology). Breathing harder made people breathe harder, not yawn more.

So whatever yawning is for, topping up your oxygen probably isn’t it.

The brain-cooling theory

In 2007, Andrew Gallup and Gordon Gallup published a study in Evolutionary Psychology that tested a different idea: that yawning works like a cooling system for the brain (Gallup & Gallup, 2007).

The theory goes like this. A yawn is a huge stretch of the jaw plus a deep breath of air that’s usually cooler than your body. That stretch increases blood flow around the head, and the incoming air helps carry heat away. The net effect, the researchers argue, is a small drop in brain temperature, which may help you stay alert.

The cold pack experiment

The Gallups showed people videos of others yawning, a reliable way to set off contagious yawns, and changed two things:

• How people breathed. Those breathing normally or through their mouth yawned about 48% of the time. Those told to breathe only through their nose, which is thought to help cool the brain, didn’t yawn at all.
• What they held to their forehead. With a warm pack (46°C) or a room-temperature pack, people yawned 41% of the time. With a cold pack (4°C), that fell to 9%.

If yawning were just about tiredness or boredom, a cold pack on your forehead shouldn’t make much difference. It did.

The “thermal window”

If yawns cool the brain, they should be less useful when the air is as hot as your body, and less needed when it’s already freezing. Field studies have tested exactly that.

• In Tucson, Arizona, a desert climate, pedestrians shown pictures of people yawning yawned more in winter (around 22°C, 45% yawned) than in summer (around 37°C, 24% yawned) (Gallup & Eldakar, 2011).
• A 2014 study led by Jorg Massen, with Andrew Gallup among the co-authors, tested pedestrians in and around Vienna, Austria, and found the opposite end of the curve: fewer people reported yawning in a 1.4°C winter (18%) than in a 19.4°C summer (42%) (Massen et al., 2014, Physiology & Behavior).

Put together, that suggests a sweet spot. We yawn most when the air is cooler than us, but not freezing.

So why is yawning contagious?

This is where the science gets less certain. Seeing, hearing or even reading about a yawn can set you off, and plenty of other animals do it too. Popular explanations include:

• Social syncing. Yawning together might help a group shift states together, for example winding down or staying alert.
• Empathy. Some studies have suggested people yawn more in response to friends and family than strangers. Other studies haven’t found a clear link, so treat this one as “interesting, not settled”.

What nobody can tell you with confidence is exactly why it spreads. If anyone says they know for certain, they’re overselling it.

Things that seem to make you yawn less

Based on the studies above, and with the caveat that these are small experiments:

1. Breathe through your nose

In the 2007 study, nose breathing stopped contagious yawns completely. Useful in a long meeting.

2. Cool your forehead

A cold pack on the forehead cut yawning sharply. A cold drink or splash of water is the everyday version, though that exact swap hasn’t been tested.

3. Don’t overheat

A stuffy, warm room is a classic yawn trap. Cracking a window fits the theory.

Told straight

We probably don’t yawn for oxygen. The best-supported theory is that a yawn helps cool the brain, and experiments with cold packs, nose breathing and seasonal temperatures back that up. Why yawns are contagious is still an open question. And yes, you’ve almost certainly yawned at least twice by now.

Sources checked November 2026. Where something is a theory rather than proven, we’ve said so.