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Most People Use Only 10% of Their Brain Power

Whenever one of us ventures out of the Ivory Tower to give a public lecture on brain science, one of the questions we most commonly hear is: "Is it true that we only use 10% of our brains?" The look of disappointment that follows our response—"Sorry, I'm afraid not"—strongly suggests that the 10% myth is one of those hopeful truisms that refuses to die simply because it would be so darn nice if it were true. Indeed, this myth is widespread even among well-educated people. In one study, fully a third of college psychology majors estimated that we use 10% of our brain power, and remarkably, another survey revealed that even some neuroscientists agree with this claim!

Surely, none of us would turn down a hefty hike in brain power if we could achieve it. It could be the ticket to a stellar grade point average, a career promotion, or the next bestselling novel. So not surprisingly, New Age gurus and entrepreneurs have long tried to capitalize on the public's fond hopes for a self-improvement breakthrough, peddling a never-ending stream of dubious schemes and devices premised on the 10% myth. Alas, virtually nothing is ever that easy. An expert panel convened by the prestigious National Research Council concluded that, as with other miraculous self-improvement claims, there's no good substitute for hard work when it comes to getting ahead in life.

The NRC conclusion is consistent with everything we have learned about the brain. First of all, our brain has been shaped by millions of years of evolution. Brain tissue is expensive to grow and operate. At a mere 2–3% of our body weight, it consumes over 20% of the oxygen we breathe. It's implausible that evolution would have permitted the squandering of resources on a scale necessary to build and maintain such a massively underutilized organ. Moreover, if having a bigger brain contributes to the flexibility that promotes individuals' survival and reproduction—which are natural selection's "bottom lines"—it's hard to believe that any slight increase in processing power wouldn't be snapped up immediately by existing systems in the brain to enhance the bearer's chances in the continuous struggle to prosper and procreate.

Doubts about the 10% myth are also fueled by evidence from clinical neurology and neuropsychology, two disciplines that aim to understand and alleviate the effects of brain damage. Losing far less than 90% of the brain to accident or disease almost always has catastrophic consequences. Look, for instance, at the much-publicized controversy surrounding the final days of Terri Schiavo, the young Florida woman who lay in a persistent vegetative state for 15 years before dying. Oxygen deprivation following a cardiac arrest in 1990 had destroyed about 50% of her cerebrum, the upper part of the brain responsible for conscious awareness. Modern brain science equates "mind" with brain function, meaning that Ms. Schiavo (and others like her) have permanently lost the capacity for thoughts, perceptions, memories, and emotions that are the very essence of being human. Although some claimed to see signs of consciousness in Schiavo, most impartial experts found no evidence that any of her higher mental processes had been spared. If 90% of the brain is indeed unnecessary, this shouldn't have been the case.

The last century has witnessed the advent of increasingly sophisticated technologies for snooping on the brain's activity. With the aid of brain imaging techniques, such as electroencephalograms (EEGs), positron emission tomography (PET) scanners, and functional magnetic resonance imaging (fMRI) machines, researchers have succeeded in localizing a vast number of psychological functions to specific brain areas. With nonhuman animals, and occasionally with humans undergoing neurological treatment, researchers can insert recording probes into the brain. This detailed mapping has revealed no "quiet areas"—that is, brain regions lacking perception, emotion or movement. There are no brain regions awaiting "new assignments." In fact, even simple tasks generally require contributions from virtually the whole brain.

Two other firmly established principles of neuroscience also undermine the 10% myth. Areas of the brain that are unused because of injuries or disease tend to do one of two things. They either wither away—or "degenerate," as neuroscientists put it—or they're taken over by nearby areas that are on the lookout for unused territory to colonize for their own purposes. Either way, perfectly good, unused brain tissue is unlikely to remain on the sidelines for long.

All told, evidence suggests that there's no cerebral spare tire waiting to be mounted with a little help from the self-improvement industry. So, if the 10% myth is so implausible, how did it get started? Attempts to track down this myth's origins haven't uncovered any smoking guns, but a few tantalizing clues have emerged. One stream leads back to pioneering American psychologist William James in the late 19th and early 20th centuries. In one of his writings for the general public, James said he doubted that most people achieve more than about 10% of their intellectual potential. James always talked in terms of underdeveloped potential, never relating it to a specific amount of brain power. A slew of "positive thinking" gurus who followed weren't as careful, though, and "10% of our capacity" gradually morphed into "10% of our brain." Undoubtedly, the biggest boost for the self-help entrepreneurs came when journalist Lowell Thomas attributed the 10% brain claim to William James. Thomas did so in the 1936 preface to one of the bestselling self-help books of all time, Dale Carnegie's How to Win Friends and Influence People. The myth has never lost its steam since.

The popularity of the 10% myth probably also stems from misunderstandings of scientific papers by early brain researchers. In calling a huge percentage of the human cerebral hemispheres "silent cortex," early investigators may have fostered the mistaken impression that what scientists now call "association cortex" has no function. As we now know, association cortex is vitally important for language, abstract thinking, and performance of intricate sensory-motor tasks. In a similar vein, early researchers' admirably modest admissions that they didn't know what 90% of the brain did probably contributed to the myth that it does nothing. Another possible source of confusion may have been laypersons' misunderstanding of the role of glial cells, brain cells once believed to outnumber the brain's neurons ten to one. Although neurons do much of the heavy lifting, psychologically, glial cells perform essential support duties - for the neurons (although recent evidence suggests they play key communication roles in their own right).

Finally, historians of neuroscience frequently come across Albert Einstein, who is said to have explained his own brilliance by reference to the 10% myth. But a careful search by the helpful staff at the Albert Einstein archive on our behalf yielded no record of any such statement on his part. More likely than not, the promoters of the 10% myth simply seized on Einstein's prestige to further their own endeavors.

The 10% myth has surely motivated many people to strive for greater creativity and productivity in their lives, which certainly isn't a bad thing. The comfort, encouragement, and hope that it's generated almost surely help to explain its longevity. But, as the late Carl Sagan liked to remind us: If something sounds too good to be true, it probably is.

From 50 Great Myths of Popular Psychology: Shattering Widespread Misconceptions about Human Behavior by Scott O. Lilienfeld, Steven Jay Lynn, John Ruscio, and Barry L. Beyerstein. Copyright © 2010 by Scott O. Lilienfeld, Steven Jay Lynn, John Ruscio, and Barry L. Beyerstein.  This material is reproduced with permission of John Wiley & Sons, Inc.

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