‘Lucy’ Brain Myth Debunked, But What About Junk DNA?

In the movie "Lucy," Scarlett Johansson portrays a woman whose brain power is boosted tenfold when the drugs that smugglers packed into her abdomen leak into her bloodstream.

The plot rests on a premise that even director Luc Besson admits is bogus: that average humans use only 10 percent of their brain capacity.

"It's one of the most popular misconceptions in biology," Christof Koch, chief scientific officer for the Allen Institute for Brain Science, told NBC News.

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Neuroscientists say the average healthy brain has no functionless regions, although dormancy can result from injury. It's true that "smart drugs" might enhance some brain functions, such as memory or attention, but they don't work by switching on unused circuitry.

The "10 percent myth" has been around for more than a century, and it just won't die, despite what neuroscientists say. That's what makes it so appealing as a movie motif, for "Lucy" as well as for previous examples of the genre such as "Limitless" and "Transcendence."

"We always think and hear terms like, 'We only use 10 percent of our brains,' but did anyone ever imagine what it would be like if you could use more?" co-star Morgan Freeman told Reuters. "So here comes Luc imagining what could happen if you could use more."

One explanation for the origin of the 10 percent myth goes back to the early days of brain science, when researchers hooked up electrodes to different parts of the brain and watched what happen. The jolts made muscles twitch only for 10 percent of the cortex leading the researchers to conclude that the other 90 percent represented the "silent cortex."

Scientists now know that large areas of the brain are devoted to cognitive function rather than motor response. They're still filling in the details with brain-scanning technologies such as functional magnetic resonance imaging. Efforts such as the $100 million BRAIN Initiative and the $1.6 billion Human Brain Project are expected to speed up progress (although there are concerns).

Next up: The debate over junk DNA

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'Lucy' Brain Myth Debunked, But What About Junk DNA?