Jonah Lehrer marvels:

One of the most remarkable facts about the human brain is that it requires less energy (12 watts) than a light bulb. In other words, that loom of a trillion synapses, exchanging ions and neurotransmitter, costs less to run than a little incandescence. Or look at Deep Blue: when the machine was operating at full speed, it was a fire hazard, and required specialized heat-dissipating equipment to keep it cool. Meanwhile, Kasparov barely break a sweat.

The same lesson applies to Watson. I couldn’t find reliable information on its offsite energy consumption, but suffice to say it required many tens of thousands of times as much energy as all the human brains on stage combined. While this might not seem like a big deal, evolution long ago realized that we live in a world of scarce resources. Evolution was right. As computers became omnipresent in our lives – I’ve got one dissipating heat in my pocket right now – we’re going to need to figure out how to make them more efficient. Fortunately, we’ve got an ideal prototype locked inside our skull.

A reader made this point earlier in the week. Another reader's dissent:

If you are going to ask how much energy two Americans consume, you do not get a reasonable value by just asking how much food they eat. You will also consider how much electricity they require to light their rooms, how much oil was burned to transport the humans from hotel to studio, how much energy was expended growing, harvesting, transporting and preparing the food in the craft services area in the studio, etc.

Watson's energy expenditures are large but explicit, while the human energy consumption is hidden behind thousands of transactions and small components that each take their toll. Even if the cost side of the equation for the two classes of contestant favored the humans you must also remember that the benefit side is not equivalent between the two. A human can also only answer a handful of questions every minute while Watson could answer thousands per second; it would take an entire army of Kens and Burts to provide the same benefit that a single Watson cluster can provide.

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