A new study by a group of Spanish scientists examined how various distractions impaired your ability to drive well. So they strapped a bunch of drivers into a Citroen, had them drive around a course while engaging in a set of distracting activities -- such as talking on a mobile phone or having a conversation. As we'd expect by now, such external activities -- or "exogenous" behavior, as they call it -- had a negative effect, decreasing one's ability to drive well by about 30 per cent.

But here's the interesting thing: Internal things -- like thinking deeply about a problem -- were just as bad. An "endogenous" activities, like meditating on the state of the Dow, can make you just as likely to mow down a nice old granny at the crosswalk. From MSNBC:

Thoughts that require visualizing other spaces also can be distracting, especially if it requires visualizing motion, which can clash with the motion of the car. For example, Nunes says, trying to think about navigating your way through a complex road map may require a lot of effort if you think about it in terms of motion. You may be better off trying to visualize your path as a still image.

(Thanks to Techdirt Wireless News for finding this one!)