I have a fondness for collecting brain lore–memes about the wonders of the human brain that race around the world for decades. The classic of brain lore is the “ten-percent myth.” As I wrote here, people often claim we only use ten percent of our brain, implying that we’d be supergeniuses if we could just switch on the rest. But that’s just based on a misinterpretation of some studies in the 1930s. Actually, the energy consumed by the cortex is only enough to power one percent of its neurons at any time.
In a press release descibing the work of Stanford bioengineer Kwabena Boahen, I stumbled on another meme:
According to Boahen, the brain is capable of performing 10 quadrillion (that’s 10 to the 16th) “calculations,” or synaptic events, per second using only 10 watts of power. At this rate, he says, a computer as powerful as the human brain would require 1 gigawatt of power.
I searched for the origin of this meme, and discovered Paul Valery, an early 20th century poet and essayist. He declared:
The ultimate “computer,” our own brain, uses only ten watts of power — one-tenth the energy consumed by a hundred-watt bulb.
It’s a claim that falls in that gray zone, the intersection of cool and crazy. So to see if it was actually true, I asked Bill Leonard, an expert on the evolution of human brains at Northwestern University. He responded thusly:
This is really interesting. The 10 watt estimate looks pretty close to being correct — perhaps a bit on a the low side, but certainly in the ballpark.
In terms of calories, here is how the 10 watts translate:
10 watts = 10 joules/sec = 207 kcal/day for the brain
At 200-210 kcals, this is enough energy to support a brain of about 1000 grams, at the low end of the modern human range.
For an average size human brain — 1300 -1400 grams — the costs would be a bit higher — between 250-300 kcal/day. However, this would only up the “wattage” to about 15.
So there you go. One urban myth survives the cold scrutiny of reason! Pass it on in the full confidence that it’s true (not to mention amazing).
Related Topics
Go Further
Animals
- Octopuses have a lot of secrets. Can you guess 8 of them?
- Animals
- Feature
Octopuses have a lot of secrets. Can you guess 8 of them? - This biologist and her rescue dog help protect bears in the AndesThis biologist and her rescue dog help protect bears in the Andes
- An octopus invited this writer into her tank—and her secret worldAn octopus invited this writer into her tank—and her secret world
- Peace-loving bonobos are more aggressive than we thoughtPeace-loving bonobos are more aggressive than we thought
Environment
- Listen to 30 years of climate change transformed into haunting musicListen to 30 years of climate change transformed into haunting music
- This ancient society tried to stop El Niño—with child sacrificeThis ancient society tried to stop El Niño—with child sacrifice
- U.S. plans to clean its drinking water. What does that mean?U.S. plans to clean its drinking water. What does that mean?
- Food systems: supporting the triangle of food security, Video Story
- Paid Content
Food systems: supporting the triangle of food security - Will we ever solve the mystery of the Mima mounds?Will we ever solve the mystery of the Mima mounds?
History & Culture
- Strange clues in a Maya temple reveal a fiery political dramaStrange clues in a Maya temple reveal a fiery political drama
- How technology is revealing secrets in these ancient scrollsHow technology is revealing secrets in these ancient scrolls
- Pilgrimages aren’t just spiritual anymore. They’re a workout.Pilgrimages aren’t just spiritual anymore. They’re a workout.
- This ancient society tried to stop El Niño—with child sacrificeThis ancient society tried to stop El Niño—with child sacrifice
- This ancient cure was just revived in a lab. Does it work?This ancient cure was just revived in a lab. Does it work?
Science
- The unexpected health benefits of Ozempic and MounjaroThe unexpected health benefits of Ozempic and Mounjaro
- Do you have an inner monologue? Here’s what it reveals about you.Do you have an inner monologue? Here’s what it reveals about you.
- Jupiter’s volcanic moon Io has been erupting for billions of yearsJupiter’s volcanic moon Io has been erupting for billions of years
- This 80-foot-long sea monster was the killer whale of its timeThis 80-foot-long sea monster was the killer whale of its time
Travel
- How nanobreweries are shaking up Portland's beer sceneHow nanobreweries are shaking up Portland's beer scene
- How to plan an epic summer trip to a national parkHow to plan an epic summer trip to a national park
- This town is the Alps' first European Capital of CultureThis town is the Alps' first European Capital of Culture
- This royal city lies in the shadow of Kuala LumpurThis royal city lies in the shadow of Kuala Lumpur