Your brain is used to trying to win rock, paper, scissors. And so if you happen to see rock coming down, it's much easier to adjust your throw mid-flight to shoot paper than it is to adjust your throw to scissors (both, by the way, are cheating).

Researchers measured this by showing subjects a string of RPS symbols on a computer screen, with a symbol every 1.5 seconds. The researchers had one group respond to the images by shooting winning symbols and another group respond by intentionally shooting losing symbols. To lose, subjects' prefrontal cortexes had to squirt some serious oxyhemoglobin to override the natural impulse to win and reaction times were slower. This is executive function overriding impulse.

Speaking of games and executive function, it is specifically this prefrontal ability to override impulse that is lacking in pathological gamblers, as well as in populations with alcohol dependence and Tourette syndrome.

Here's the rub: tomorrow I'll post a guide to WINNING rock, paper, scissors. Oh yes, the world will be yours.

For now, what kind of geek are you? If input="math geek", goto

your nearest bookstore and purchase a copy of Geek Logik: 50 Foolproof

Equations for Everyday Life. If you're a full featured, renaissance

geek of all trades looking for a good time at others' expense, consider a

copy of The Geeks' Guide to World Domination:

Be Afraid Beautiful People. And if you're a geek of the mind,

consider preordering a copy of my new book, Brain Candy: Science,

Paradoxes, Puzzles, Logic and Illogic to Nourish Your Neurons

(shipping August 3rd).