If you offer someone "a penny for their thoughts," how good a deal might you be getting? A study conducted at the University of Leicester has sought to shed some light on the value of our brainpower, finding a single penny to be worth to precisely three hours, seven minutes and 30 seconds worth of thinking.

Osarenkhoe Uwuigbe, a Natural Sciences student at the University of Leicester’s Centre for Interdisciplinary Science, used a number of assumptions about the brain and the economics of thinking to arrive at this final figure. Based on the fact that the average human body produces around 100 watts of power, Uwuigbe calculated that the power required by a human brain to generate thoughts to be around 20 percent of this, or 20 watts.

Uwuigbe used English pennies for the currency and when calculating the cost of power, he used the price per kilowatt hour (kWh) offered by UK energy providers as a reference point. He chose 16 pence per kWh because it lies within the range normally charged by these companies.

Now comes the maths. Assuming that all the power consumed by the brain is used on thinking, 20 W, or 1/50 kW is what it takes to keep our minds ticking. So if a penny buys 1/16th of a kWh and if you can speak as fast as you can think, this works out to (1/16) ÷ (1/50) = 3.12 hours, or 3 hours, 7 minutes, and 30 seconds.

This makes for a very long, but affordable monologue.

"This model is likely to be an underestimate as power required for the brain to operate does not necessarily translate to power used in thought," says Uwuigbe. "The brain has several autonomic functions it carries out during thought processing and as a result thought processing could not take 100 percent of the power consumption of the brain. Furthermore, it is unlikely that it is possible to think as fast as you speak due to delay caused by biological constraints such as conduction velocity of nerves carrying the signal from the brain to the mouth, the release of Ca2+ ions during muscle contraction of the tongue and lips and so on."

The study was published in the peer-reviewed student Journal of Interdisciplinary Science Topics.