Columns

Dear Science

Heat Makes You, Objectively, Dumb

by Jonathan Golob

Dear Science,

When the weather is hot (like it is today), I feel stupid. It's like my brain just melts and I drop about 30 IQ points. Is this actually possible, or is it all psychological? I spent about 15 minutes buying a two-liter bottle of soda today, and it wasn't because I had to wait in line at the register—it was because I couldn't operate the self-checkout to save my life. Can I blame this on the heat, or is it all on me?

Hot Head

Science is trying to write this column on a really scorching day in Seattle. It's taking forever. This paragraph has been rewritten four times—eyes thick, fingers clumsy, and attention wandering throughout the room, street, city. Hot Head, you aren't alone; heat makes us all stupid and slow.

Our brains have a pretty potent cooling system. All the blood pulsing through your brain delivers oxygen first, and then whisks away the heat generated when the oxygen is used with sugar to make energy. The blood then runs up through the bridging veins right to the top of the head—positioned like an internal Mohawk. The heat then dumps out right there, causing sweat to run right down your face. (Consider this yet another reason why bald men should be respected.) On a normal day, this all works splendidly. On a hot day, where the top of your head is probably being baked, your blood temperature creeps upward, making the inside of your skull somewhat like a crappy car that needs the heater to be on in order to run in the summer. Any brain temperature above 40 degrees Celsius, easily reached if you're doing anything active on a hot day, starts wreaking havoc.

The monoamine neurotransmitters—serotonin, dopamine, and norepinephrine—seem to have a hard go of things as the temperature climbs. The neuroscientists cannot agree what exactly goes on with serotonin (and mutter about not being able to slice open the brains of overheated athletes to get at a definitive answer). Taking the drug buspirone, which acts like serotonin in the brain, makes athletes fatigue more quickly in the heat—so don't go grab your Prozac and hope to make it all better.

Dopamine is critical for controlling movement—and not seeing and hearing things that aren't actually there. Dopamine, in the right amounts in the right places of the brain, is your friend. Heat seems to do something with dopamine levels and distribution in the brain. The closest we can really get to understanding all of this is in the brains of overheated and tired rats; once rat brains hit that magic 40 degrees Celsius, they start to shut down. That's all to say you should ice-pack your neck if you want to think in the next heat wave.

Swelteringly Yours,

Science

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