If that cartoon light bulb that appears over your head when you get an idea were ever real, how big would it be?

The average human brain produces the energy equivalent of a 10-watt electric bulb, according to Amazing Facts About the Body, a book published by Doubleday and Co.

However, unlike electricity, which travels near the speed of light (almost 300 000 kilometres per second), the brain's impulses travel only 320 kilometres per second.

Translated that means: the speed of thought is about the same as a speed limit of 90 kilometres per hour.

Scientists believe the relatively slow rate is geared to the body's ability to respond and to avoid what otherwise would become an electrical brain storm that would resemble an epileptic fit.

(Source: Amazing Facts About the Body)