Tyler Cowen tweeted:

Why do chess players hold their heads hard, with their hands, when they are thinking? If it works, why don’t more thinkers do it?

To prevent overheating of course.  You’ll notice that they typically extend their fingers and cover their foreheads which is the hottest part.  They are maximizing surface area in order to increase heat dissipation.

Here is a suggestion for how to super-cool your cranium and over-clock your brain.  On a more serious note, here is a pipe that is surgically implanted in the skull of epileptics to reduce the intensity of seizures.