Acclaimed neuroscientist David Eagleman has written a book, The Brain – The Story of You, that educates us as to the nature of the human brain and how it defines your identity. The author uses the latest in scientific research to answer five fundamental questions related to our existence:

  • Who Am I?
  • What is Reality?
  • Who is in Control?
  • How Do I Decide?
  • Do I Need You?

Eagleman does a great job describing the human brain, made up of billions of cells and trillions of synaptic connections, and how this defines you. The first chapter does an excellent job describing how the brain develops throughout your life and how this defines who you are at this very moment.

Birth

At birth we are helpless and totally dependent on others to survive. This is in contrast to the majority of mammals on the planet that are born independent soon after they’re born. Eagleman writes, “Baby animals develop quickly because their brains are wiring up according to a largely programmed routine”. In contrast, “humans are able to thrive in many different environments” because the “human brain is born remarkably unfinished”, allowing it to “be shaped by the details of life experience”. The young brain “slowly molds to its environment. It’s “livewired””.

Childhood

By age two, a child has “over one hundred trillion synapses, double the number an adult has”. Entering childhood, “50 percent of your synapses will be pared back”.  It is fascinating to learn that “you become who you are not because of what grows in your brain, but because of what is removed”.  Importantly, “throughout our childhoods, our local environments refine our brain, taking the jungle of possibilities and shaping it back to correspond to what we’re exposed to”.  Eagleman writes that, through the pruning process of the brain’s synapses, the brain shapes itself to its environment. “If developing brains are not given the proper, “expected” environment – one in which a child is nurtured and looked after – the brain will struggle to develop normally”.  This points to the crucial role of parenting in the brain’s development.  Research is clear that “we are exquisitely sensitive to our surroundings…Because of the wire-on-the-fly strategy of the human brain, who we are depends heavily on where we’ve been”.

Teen Years

Eagleman writes that “the teen years are a period of important neural reorganization and change”. The teenage brain undergoes monumental changes:

  • Self-consciousness – An area of the brain called the prefrontal cortex becomes active, particularly in social situations that carry with them emotional significance. Eagleman writes, “At this point, social situations carry a lot of emotional weight, resulting in a self-conscious stress response of high intensity”.
  • Self-evaluation – Thinking about oneself and developing a sense of self.
  • Risk-taking – “Risky behaviors are more tempting to the teen brain than to the adult brain”.
  • Emotional control – “Teens are not only emotionally hypersensitive, but also less able to control their emotions than adults”.

Eagleman concludes that the changing brain in teen years leads teenagers to “be more self-conscious, more risk-taking and more prone to peer-motivated behavior”.

Adulthood

Eagleman writes, “By the time we’re twenty-five years of age, the brain transformations of childhood and adolescence are finally over”. In adulthood life experiences continue to change the brain (due to its neuroplasticity). “Everything you’ve experienced has altered the physical structure of your brain – from the expression of genes to the positions of molecules to the architecture of neurons. Your family of origin, your culture, your friends, your work, every movie you’ve watched, every conversation you’ve had – these have all left their footprints in your nervous system. These indelible, microscopic impressions accumulate to make you who you are, and to constrain who you can become”.

In adulthood, Eagleman points out that our memories are not overly reliable. “Rather than memory being an accurate video recording of a moment in your life, it is a fragile brain state from a bygone time that must be resurrected for you to remember”.  Furthermore, “Our past is not a faithful record. Instead it’s a reconstruction and sometimes it can border on mythology”.

In conclusion, Eagleman states that “the meaning of something to you is all about your webs of association, based on the whole history of your life experiences”. In the end, “each of us is on our own trajectory – steered by our genes and our experiences – and as a result every brain has a different internal life. Brains are as unique as snowflakes”.