Fact or fiction: We only use 10 per cent of our brain

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Fact or fiction: We only use 10 per cent of our brain

It has been a popular belief for over a century now that humans aren’t fulfilling our intellectual potential.

Self-improvement gurus, advertisers and possibly even Albert Einstein have stated that 90 per cent of our brains are sitting idle. The idea has proved popular in Hollywood too, with Luc Besson’s latest film Lucy using it as a major plot device.

In the film Samuel Norman, a fictional neuroscientist played by Morgan Freeman, says: “It is estimated most human beings only use 10 per cent of their brains’ capacity. Just imagine if we could access 100 per cent.”

Is the claim we are only using 10 per cent of our brains fact or fiction?

ABC Fact Check asks the experts.

Where does it come from?

A 2013 survey by the Michael J Fox Foundation for Parkinson’s Research found almost two-thirds of Americans believe we only use 10 per cent of our brains but exactly where the idea comes from is hard to pin down.

Behavioural neurophysiologist Eric Chudler, the executive director of the Center for Sensorimotor Neural Engineering at the University of Washington in Seattle, says the theory was popularised in the early 20th century by psychologist William James in an influential 1907 essay “The Energies of Men”.

In it Professor James wrote, “as a rule men habitually use only a small part of their powers which they actually possess and which they might use under appropriate conditions”.

The 1937 foreword to one of the first self-improvement books, “How to Win Friends and Influence People” by personal development advocate Dale Carnegie, referred to Professor James’ claim.

“Professor William James of Harvard used to say that the average person develops only 10 per cent of his latent mental ability,” the foreword, written by Lowell Thomas, says.

There is also evidence to suggest that the work of brain researchers in the first half of the 20th century helped popularise the idea.

Karl Lashley, elected president of the American Psychological Association in 1929, did experiments on rats which found they only needed small amounts of the brain to conduct a range of tasks including running a maze.

Expanding our minds

The adult human brain weighs about 1.5 kilograms and includes nerve cells called neurons. The way those cells connect and communicate is the basis of brain function.

Con Stough, Professor of Cognitive Neuroscience and Psychology at Swinburne University of Technology in Melbourne, says we make new connections in our brains when we learn.

“There are up to ten billion cells and each can make new connections, sometimes each cell can make hundreds of connections, so this is really where there could be plasticity and new possibilities,” Professor Stough told Fact Check.

Ashley Bush from Melbourne’s Florey Institute of Neuroscience and Mental Health says “awareness” such as thoughts and calculation might indeed only represent 10 per cent of the complex operations of the brain at any one time.

But Professor Bush says the rest of the human brain has plenty to do and is constantly performing unconscious processes.

“The brain is constantly vigilant but we are not aware of this… Even when asleep, most of the brain is active,” he says.

The brain regulates everything from our heart rate and our senses to our dreams and emotions – so the brain is kept very busy.

“We use different parts of our brains in different ways when we do different things, but there are no parts of the brain sitting there unused,” Dr Chudler told Fact Check.

Dr Chudler says people can always learn new ideas and new skills, but not because we are tapping into some unused part of the brain – what’s actually happening is that we are forming new or stronger connections between nerve cells.

Mapping brain activity

According to Professor Bush, neurologists visualise brain activity with scans like functional magnetic resonance imaging (FMRI) and know the brain activates different parts of itself when called upon for various tasks.

FMRI has revolutionised understanding of brain function in the past twenty years, showing which parts of the brain are experiencing greater neural activity as they consume more oxygen from the blood.

FMRI scans also reveal that several areas of the brain are used for any given task.

Other methods of measuring brain activity include positron emission tomography (PET) scans, which use an injected radioactive compound to highlight areas of the brain with the most activity.

There are a number of international projects underway seeking to comprehensively “map” the human brain, the largest being the international Human Connectome Project (HCP).

It aims to achieve “A deeper understanding of human brain connectivity and its variability [which] will provide valuable insights into what makes us uniquely human and what accounts for the great diversity of behavioural capacities and repertoires in healthy adults”.

The Human Brain Atlas from Michigan State University allows you to watch movies of each section of the human brain functioning.

The brain myth

None of the experts consulted by Fact Check supported the notion we are only using 10 per cent of our brains.

Professor Bush says the idea that we can tap into a dormant 90 per cent is “hogwash”.

Professor Stough agrees there’s “no truth” to the 10 per cent claim. But he also says the brain does have “some redundancy” in it.

“We are still understanding how the brain works and how we learn, as well as the plasticity of the brain – which is fascinating,” he says.

Dr Chudler, who has written extensively on the subject, says the claim is simply a myth.

Fact or fiction?

Experts Fact Check spoke to agree that there is potential to train the human brain to learn new skills and ideas but the idea that we only use 10 per cent of our brain capacity is, like the film Lucy, pure fiction.

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