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Do You Use Only 10% of Your Brain?

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We may be biased, but we think the human brain is pretty special. All this week, mentalfloss.com is celebrating this miracle organ with a heap of brain[y] stories, lists, and videos. It all leads up to Brain Surgery Live With mental_floss, a two-hour television event hosted by Bryant Gumbel. The special airs Sunday, October 25 at 9 p.m. EST on the National Geographic Channel.

The simple answer is: No.

This myth is so prevalent that it is unquestioningly accepted as a pivotal plot point in movies, a motivational tactic for self-improvement, or justification for claims about ESP and other supposed untapped abilities of the human mind. A 2013 poll surveying over 2000 Americans found that 65 percent believed the 10 percent myth. A 2007 study in the British Medical Journal (BMJ) found that even some doctors weren't immune to the fallacy. But the truth is that everyone uses 100 percent of their brain.

Proving this idea wrong is relatively easy with modern technology. PET and fMRI scans show that even when we're sleeping, our entire brain is active on some level. Our observations of individual neurons or cells reveal no inactive areas of the brain. Metabolic studies of cellular metabolism in the brain show consistent activity as well. "Evidence from studies of brain damage, brain imaging, localization of function, microstructural analysis, and metabolic studies show that people use much more than 10 percent of their brains," according to the BMJ paper. "No area of the brain is completely silent or inactive."

But even before imaging techniques allowed scientists to definitively debunk this myth, how did it arise in the first place? And why has it held on into the era of such increased understanding of how the brain works?

Some attribute its origin to the prominent philosopher and psychologist William James, who in 1907 wrote in The Energies of Man, "We are making use of only a small part of our possible mental and physical resources." He probably meant that we all have untapped potential. Twenty-nine years later, in the introduction to Dale Carnegie's How To Win Friends and Influence People, Lowell Thomas wrote, presumably referencing that quote, "Professor William James of Harvard used to say that the average man develops only ten per cent of his latent mental ability."

From here, the sentiment seems to have spun off; versions of it found use in the science fiction and spiritual communities. It didn't help matters that in the 1920s and '30s, prominent psychologist Karl Lashley attempted to isolate regions of the brain by removing areas of the cerebral cortex in rats. When he found they were still able to learn and remember specific tasks, it contributed to the idea that there are large swatches of "inactive" brain mass. We know now the brain's plasticity allows it to recover from such injury and compensate for the loss. That's the very opposite of inactive. 

Decades later, the myth has persevered because of the attractive possibility it seems to present. It absolves us for not reaching our full potential, offers a persistent insecurity for self-help gurus to appeal to, and provides a pseudo-scientific explanation for the limits of human comprehension. 

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Big Questions
Why Do Cats 'Blep'?
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As pet owners are well aware, cats are inscrutable creatures. They hiss at bare walls. They invite petting and then answer with scratching ingratitude. Their eyes are wandering globes of murky motivations.

Sometimes, you may catch your cat staring off into the abyss with his or her tongue lolling out of their mouth. This cartoonish expression, which is atypical of a cat’s normally regal air, has been identified as a “blep” by internet cat photo connoisseurs. An example:

Cunning as they are, cats probably don’t have the self-awareness to realize how charming this is. So why do cats really blep?

In a piece for Inverse, cat consultant Amy Shojai expressed the belief that a blep could be associated with the Flehmen response, which describes the act of a cat “smelling” their environment with their tongue. As a cat pants with his or her mouth open, pheromones are collected and passed along to the vomeronasal organ on the roof of their mouth. This typically happens when cats want to learn more about other cats or intriguing scents, like your dirty socks.

While the Flehmen response might precede a blep, it is not precisely a blep. That involves the cat’s mouth being closed while the tongue hangs out listlessly.

Ingrid Johnson, a certified cat behavior consultant through the International Association of Animal Behavior Consultants and the owner of Fundamentally Feline, tells Mental Floss that cat bleps may have several other plausible explanations. “It’s likely they don’t feel it or even realize they’re doing it,” she says. “One reason for that might be that they’re on medication that causes relaxation. Something for anxiety or stress or a muscle relaxer would do it.”

A photo of a cat sticking its tongue out
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If the cat isn’t sedated and unfurling their tongue because they’re high, then it’s possible that an anatomic cause is behind a blep: Johnson says she’s seen several cats display their tongues after having teeth extracted for health reasons. “Canine teeth help keep the tongue in place, so this would be a more common behavior for cats missing teeth, particularly on the bottom.”

A blep might even be breed-specific. Persians, which have been bred to have flat faces, might dangle their tongues because they lack the real estate to store it. “I see it a lot with Persians because there’s just no room to tuck it back in,” Johnson says. A cat may also simply have a Gene Simmons-sized tongue that gets caught on their incisors during a grooming session, leading to repeated bleps.

Whatever the origin, bleps are generally no cause for concern unless they’re doing it on a regular basis. That could be sign of an oral problem with their gums or teeth, prompting an evaluation by a veterinarian. Otherwise, a blep can either be admired—or retracted with a gentle prod of the tongue (provided your cat puts up with that kind of nonsense). “They might put up with touching their tongue, or they may bite or swipe at you,” Johnson says. “It depends on the temperament of the cat.” Considering the possible wrath involved, it may be best to let them blep in peace.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Big Questions
What Is Foreign Accent Syndrome?
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One night in 2016, Michelle Myers—an Arizona mom with a history of migraines—went to sleep with a splitting headache. When she awoke, her speech was marked with what sounded like an British accent, despite having never left the U.S. Myers is one of about 100 people worldwide who have been diagnosed with Foreign Accent Syndrome (FAS), a condition in which people spontaneously speak with a non-native accent.

In most cases, FAS occurs following a head injury or stroke that damages parts of the brain associated with speech. A number of recent incidences of FAS have been well documented: A Tasmanian woman named Leanne Rowe began speaking with a French-sounding accent after recovering from a serious car accident, while Kath Lockett, a British woman, underwent treatment for a brain tumor and ended up speaking with an accent that sounds somewhere between French and Italian.

The first case of the then-unnamed syndrome was reported in 1907 when a Paris-born-and-raised man who suffered a brain hemorrhage woke up speaking with an Alsatian accent. During World War II, neurologist Georg Herman Monrad-Krohn compiled the first comprehensive case study of the syndrome in a Norwegian woman named Astrid L., who had been hit on the head with shrapnel and subsequently spoke with a pronounced German-sounding accent. Monrad-Krohn called her speech disorder dysprosody: her choice of words and sentence construction, and even her singing ability, were all normal, but her intonation, pronunciation, and stress on syllables (known as prosody) had changed.

In a 1982 paper, neurolinguist Harry Whitaker coined the term "foreign accent syndrome" for acquired accent deviation after a brain injury. Based on Monrad-Kohn's and other case studies, Whitaker suggested four criteria for diagnosing FAS [PDF]:

"The accent is considered by the patient, by acquaintances, and by the investigator to sound foreign.
It is unlike the patient’s native dialect before the cerebral insult.
It is clearly related to central nervous system damage (as opposed to a hysteric reaction, if such exist).
There is no evidence in the patient’s background of being a speaker of a foreign language (i.e., this is not like cases of polyglot aphasia)."

Not every person with FAS meets all four criteria. In the last decade, researchers have also found patients with psychogenic FAS, which likely stems from psychological conditions such as schizophrenia rather than a physical brain injury. This form comprises fewer than 10 percent of known FAS cases and is usually temporary, whereas neurogenic FAS is typically permanent.

WHAT’S REALLY HAPPENING?

While scientists are not sure why certain brain injuries or psychiatric problems give rise to FAS, they believe that people with FAS are not actually speaking in a foreign accent. Instead, their neurological damage impairs their ability to make subtle muscle movements in the jaw, tongue, lips, and larynx, which results in pronunciation that mimics the sound of a recognizable accent.

"Vowels are particularly susceptible: Which vowel you say depends on where your tongue is in your mouth," Lyndsey Nickels, a professor of cognitive science at Australia's Macquarie University, wrote in The Conversation. "There may be too much or too little muscle tension and therefore they may 'undershoot' or 'overshoot' their target. This leads to the vowels sounding different, and sometimes they may sound like a different accent."

In Foreign Accent Syndromes: The Stories People Have to Tell, authors Nick Miller and Jack Ryalls suggest that FAS could be one stage in a multi-phase recovery from a more severe speech disorder, such as aphasia—an inability to speak or understand speech that results from brain damage.

People with FAS also show wide variability in their ability to pronounce sounds, choose words, or stress the right syllables. The accent can be strong or mild. Different listeners may hear different accents from the speaker with FAS (Lockett has said people have asked her if she's Polish, Russian, or French).

According to Miller and Ryalls, few studies have been published about speech therapy for treating FAS, and there's no real evidence that speech therapy makes a difference for people with the syndrome. More research is needed to determine if advanced techniques like electromagnetic articulography—visual feedback showing tiny movements of the tongue—could help those with FAS regain their original speaking manner.

Today, one of the pressing questions for neurologists is understanding how the brain recovers after injury. For that purpose, Miller and Ryalls write that "FAS offers a fascinating and potentially fruitful forum for gaining greater insights into understanding the human brain and the speech processes that define our species."

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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