Our mind is a mysterious place, but we're learning more than ever about our gray matter. Here are myth-busting truths, new research, and surprising factoids you didn't know about the human thinking machine.
You use way more than 10 per cent of your brain
When it comes to favourite facts you've always believed that are actually false, the idea that you only use 10 per cent of your brain is right up there. One survey found that half of college-educated people believe it to be true — but it's not.
"We use every part of the brain," says Rawan Tarawneh, MD, an assistant professor of neurology in the division of cognitive neurology at The Ohio State University. "While brain regions are not necessarily all active at the same time, all brain regions are utilised to some extent over the day, depending on what we are doing — for example, reading, trying to solve a math problem, driving, talking on the phone, or sleeping."
No one is either "left-brained" or "right-brained"
Even though we are right- or left-handed, it doesn't mean we are right- or left-brained. The myth of having a dominant brain hemisphere may have come from experiments performed in the 1960s on people who'd had the connections (the "corpus callosum") between their two halves severed. But most of us have brains that aren't split in two, and thus function as one.
"Research shows that almost all brain functions require the interaction of both hemispheres for these functions to be carried out accurately," Dr Tarawneh says. Each half may perform separate functions within a task — our ability to express and understand language happens in the left hemisphere, but other aspects of language processing, such as intonations, rhythm and stress of words, occurs in the right — but this is true for everyone, she notes.
Men and women don't learn differently
There are many differences between men and women, but it doesn't mean that the sexes aren't equal in their learning capabilities. "On average, men have larger brain volumes than women, while women have thicker cortices than men," Dr Tarawneh says. "The differences are not just anatomical — men's and women's brains seem to be wired differently to some extent."
She points to research by Diane Halpern, PhD, who found that women do better with verbal and writing ability, and men better with problem-solving and visuospatial skills. But, there may be a social component to this, and other research has shown both sexes performing equally in mathematics. "Men's and women's brains are more alike than they are different, and there is a lot of variability between individuals of the same gender," Dr Tarawneh says.
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Size doesn't matter — or does it?
Another ongoing debate is how your brain's size impacts your smartness. "The size of the brain is not linked to intelligence or learning new material," Dr Tarawneh says. Comparing the brains of great thinkers, writers and mathematicians after autopsy hasn't yielded conclusive evidence that their size has a correlation to intelligence.
Even among different species, research has shown that when it comes to brain-to-body ratio, the "smarter" animals don't always have bigger brains. However, scientists have come up with an "encephalisation quotient" that compares animals based on their relative body size — and humans finally come out on top.
The size of our brains cause us to be born "too soon"
The theory of the "fourth trimester" suggests that babies are born when their bodies are still very fragile in order to allow for their relatively large brains to have room to be delivered. "I always tell my patients that all babies are born too soon," says Harvey Karp, MD, author of The Happiest Baby on the Block and creator of the "smart sleeper" SNOO.
"Think about it — a horse can walk on the very first day of life, but by comparison, human babies are super immature. They can't walk, run, or even burp without help from Mom or Dad." A horse's survival depends on his body, but human survival depends on our brain. "So, our species evolved to evict our little genius babies from the womb three months early — before their heads get so big that they risk getting stuck in the birth canal," Dr Karp says.
Brain folds have function
Although Dr Tarawneh says that the number of folds, or gyri, in the human brain doesn't always equal intelligence, they do have a purpose. The folds allow for more surface area on the outer layer, or cortex, of the brain.
"The cortex is the computational part on the outer surface of the brain, where the majority of the brain cells are," Dr Tarawneh says. Monkeys and dolphins also have wrinkly brains, whereas the surface of mice brains are smooth. But, scientists are still researching how these folds develop.
The nature of intelligence isn't known
You can fake being smart, but what really makes us intelligent, if not brain size and folds? "Although we still do not know all of the biological processes that explain intelligence, intelligent people probably have better connections between the neurons, referred to as synapses, and their neurons have stronger networks in certain brain regions that allow the brain cells to communicate with each other more efficiently," Dr Tarawneh says.
She notes that anatomy may have something to do with it, as some studies suggest more intelligent people may have thicker cortices (the outer part of the two hemispheres), particularly in some parts such as the parietal lobe.
IQ is not fixed
Although the origins of intelligence are still being researched, it does seem clear that IQ, or intelligence quotient, is not fixed — it can change throughout your life. In fact, some experts argue that there's no such as thing as "IQ" at all, but that experiences and learning, as well as the testing itself, are variable and can change over time. Studies show our nutrition and other environmental factors may also impact brain power.
"We used to think that once smart, always smart and vice versa — we now know that is wrong," says Sandra Bond Chapman, PhD, founder and chief director of the Center for BrainHealth at the University of Texas at Dallas. "Science clearly reveals that the brain and our 'smartness' are anything but fixed. We continuously shape and rewire our brain by how we think." That's one of the reasons you shouldn't tell your child, "You're so smart."
The brain changes as it ages
It's true that certain aspects of our head change — some for the worse — as we age. "As we age, our brains normally shrink in size by about one to two per cent every year after the age of 40," Dr Tarawneh says. "This occurs due to loss of brain cells, brain cells shrinking in size, and also some loss of the branches that neurons use to communicate with each other, referred to as dendrites."
But, the brain also improves as we age. Recent research has some good news — more than one-third of the neurons in the hippocampus are regularly renewed throughout life, according to a Swedish study.
In some ways we get smarter as we age
Dr Tarawneh points out that although some mental processes decline as we age, not all do. "Some of our brain functions such as short-term memory for minor details, processing speed, attention, the ability to multi-task, and visuospatial functions show some decline with healthy aging," she says. "On the other hand, language functions tend to remain well-preserved as we get older."
In fact, research from Harvard and MIT show that arithmetic skills don't peak until age 50, and vocabulary and "cumulative intelligence" (all the facts and knowledge you've acquired) peak even later, into our early 70s.
The brain can adapt
We now know that the way the brain works isn't fixed, and can "recruit" other areas to compensate for damaged parts when needed. For example, we know that in certain cases, brain injury leads to brilliance. "The brain can adapt to injury such as stroke or head trauma, a process referred to as 'brain plasticity'," Dr Tarawneh says. "The brain can 'rewire' itself so that healthy neurons can form new networks, or modify existing networks to compensate for the damaged parts of the brain."
Experiments in people who were born blind show that they use the visual parts of their brain, even though they can't see. "One of the most important discoveries in the field is that brain activity can stimulate the process (of revising connections between neurons), which is referred to as activity-dependent plasticity," she says. "Therefore, brain exercises and rehabilitation is a crucial step in recovery from brain injury, as it allows the brain to 're-learn' functions that were lost due to trauma, in a way that is very similar to what is seen in early brain development."
The brain doesn't mature until age 25
Although we've already legally become an adult, our brains aren't fully grown up until around age 25 according to science. And your brain can continue to grow long past your 20s. Dr Tarawneh says the brain matures from back to front, with the "prefrontal cortex" the last to finish developing. "The prefrontal cortex is responsible for higher-order thinking — referred to as executive function — such as judgment and problem-solving, decision-making, complex planning, organised thinking, personality development and impulse control," she says.
"The reward centres of the brain are the most active during adolescence but are back to normal levels of activity by the mid-20s, so individuals become less sensitive to peer pressure and much better at risk management during their 20s compared to the adolescent years."
Brain games don't make you smarter
You might think getting good at Sudoku or doing the daily crossword puzzle will enhance your brain's capabilities, but sadly this isn't the case. "If you do a lot of crossword puzzles, you can get better and better at completing crossword puzzles," says Dr Chapman. "The limitation is that the mental effort spent on this challenge, while building vocabulary, is unlikely to expand your higher-level reasoning abilities, such as decision-making, planning, and judgment."
Another example: Even if you get really good at remembering where the red cube was on a screen, it doesn't mean that you'll always remember where you put your car keys. A group of scientists actually have signed a statement refuting the claim that brain games can slow cognitive decline, saying there is, as yet, no scientific evidence that they do.
You can strengthen your brain
Although brain games may not supercharge your thinking cap, you can train your brain by focusing on broader, more dynamic skills. "The best news is that we can do things to counter age-related brain decline and strengthen our 'smartness' into late life – especially when it comes to innovative problem solving and deeper level thinking," Dr Chapman says.
"Reasoning and innovative thinking contribute to the intellectual capacity needed to respond effectively to our constantly changing real-life demands." For example, learning a new language, a musical instrument, or other new hobbies have been shown to increase brain function.
Social interaction is good for the brain
If you want to remain sharp as you get older, it's not just about gaining knowledge but about social stimulation too. "Research suggests that meaningful social activities actually maintains or increases brain function," says Anthony Cirillo, president of the healthcare consulting firm The Aging Experience.
"The memory centre in the brains of seniors maintained their size and, in men, grew modestly after two years in a programme that engaged them in meaningful and social activities." So volunteering, visiting with friends and family, and staying active in social groups can actually help your brain as you age.