Editor's note: Elaine Fox, author of "Rainy Brain, Sunny Brain: How to Retrain Your Brain to Overcome Pessimism and Achieve a More Positive Outlook," is a visiting research professor at the University of Oxford. Follow her on Twitter at @ProfElaineFox.
(CNN) -- Why do some people flourish, seemingly resilient to all that life throws at them, while others are vulnerable and at risk of serious problems like anxiety and depression?
My approach to unraveling this mystery has been to probe the minds of both the vulnerable and the resilient with the traditional tools of cognitive psychology.
Flashing positive and negative images on a computer screen so fast that they duck beneath the radar of consciousness gives us a momentary glimpse of what captivates the unconscious mind. And what have we learned?
Techniques like this tell us that the mind of the pessimist is drawn imperceptibly toward the negative while the upbeat and positive is a magnet for the optimist.
Crucially, these differences -- whether we turn toward the bright side of life or the dark -- can be traced to specific patterns of activity within the brain itself. Bundles of nerve fibers connecting our "thinking" brain with ancient regions that control our primeval "feeling" brain make up two sides of our emotional mind.
The "rainy" brain part highlights the negative, while our "sunny" brain draws us toward the positive. Of course, both elements are essential to a healthy and successful life, and it's the checks and balances between these two systems that ultimately make you you and me me. In short, it's our emotional mind that gives meaning to our lives by tuning us in to what really matters.
At the very root of what captivates our emotional mind are two polar opposite constructs: fear and pleasure.
These biological motivators kick-start our rainy and sunny brain circuits, which, in turn, underlie our pessimistic and optimistic mindsets. These brain systems infuse our mind with meaning, make us aware of what might harm us, alert us to what might go wrong, draw us toward what's good for us and highlight the sheer joys and pleasures of living.
Take the following: You are rushing for a meeting and miss your train. You hurry to the office, finally arriving a few minutes late. When you enter the room, everybody looks up, and your boss smiles and says, "Glad you could make it."
Question: Is she being sarcastic? Or is she happy to see you? The truth is, how you interpret this situation can set the tone for the rest of your day. Cutting-edge science tells us that these ways of interpreting and analyzing the world around us can become habitual and that it is these habits of mind that make us who we are.
The good news is that the human brain has a startling capacity to change. For years, neuroscientists believed that from a young age, our brains became inflexible and neurologically set in their ways. The burgeoning field of neuroplasticity, however, has completely overturned this notion and shown us that our brains are far more flexible than we ever dared to imagine.
And I'm not just talking about superficial changes at the level of "thinking." Instead, I'm talking about real concrete change in physical structure.
Our relationship with our neurons is organic: Sure, we respond to our neurons, but our neurons respond to us, to the things we do and even the things we think, resulting in observable changes in our brain. This exquisite malleability ensures that our unique, personal experiences provide us with a customized brain with its own highly individualized sets of circuits, switches and connections.
The bottom line is that if we change our cognition, we can also reshape our brains.
Example: There are more than 25,000 streets in London, arranged in a complex maze of junctions and byways that have developed through the years. As any tourist will tell you, there is no easy symmetry as you find in New York, with its easy to navigate horizontal and vertical patterns of streets and avenues. Yet, jump in a black cab -- London's iconic taxis -- anywhere in the city, and the driver will get you to where you want to go via the shortest possible route.
Why? Because every one of them have passed what is called the Knowledge: a test of the ability to memorize and spatially navigate every one of those 25,000 streets.
Now, learning the Knowledge is one thing. But scientific studies have taken things one step further and shown that as cab drivers hone their skills, their hippocampus -- the part of the brain that deals with spatial memory and navigation -- gradually gets bigger. That's right! The more they learn, the larger this part of their brain becomes.
In other words, personal experiences and skills are reflected in the way our brains are organized.
It turns out that what's true of our knowledge is also true of our mindset. In other words, if we train our brains to be optimistic or pessimistic -- to navigate, intentionally or not, the streets and avenues of positive or negative feelings -- we change (just as cab drivers do with their spatial circuits) the emotional circuits in our brains that determine how we respond to the things that happen around us.
In my book "Rainy Brain, Sunny Brain," I discuss how genes and environments work together to influence how emotional circuits develop. Rather than being hard-wired, our social relationships and how we live play a huge role in shaping and reshaping our brains. In fact, there are now several techniques based on solid scientific evidence that allow us to begin the journey from pessimism to a more optimistic take on life.
While we need both aspects of our emotional mind -- rainy and sunny -- to live life to the full, there is abundant evidence that an optimistic take on the world, especially when linked with realism, is associated with better health, more success and a deeper sense of well-being.
The opinions expressed in this commentary are solely those of Elaine Fox.