Understanding the Brain of a Teen

Why are human babies so helpless for so long? Babies of all other animals, birds and insects get on with their lives quite quickly. It will not be an exaggeration to say that dolphins are born to swim, giraffes are born to walk and zebras are born to run. But we take a year to walk, two years to speak and many more years to fend for ourselves. 

It is because we have a different biology. That is, we have a ‘live-wired’ brain against a ‘hard-wired’ pre-programmed brain of non-humans. According to David Eagleman, author of the fascinating book ‘The Brain’, we are ‘born unfinished’. This is the trade-off between preparedness and flexibility.

In a newborn human baby’s brain, neurons are sparse and disparate. After birth, connections, called synapses, are formed between these neurons. At the rate of two million synapses per second, about one hundred trillion synapses are made by the age of two. It will be worthwhile to know here that an adult brain has half as many synapses. So between two to 25 years, neural pruning happens. Imagine a dense wild forest. And you are walking through it. Whichever direction you take you make pathways. But if these paths are not reused the forest grows over them and they are lost. This is why it is crucial to learn new skills in our brain’s formative years.

A twist in the tale happens when the brain crosses the age of twelve. As a toddler’s body becomes a teen, while hormones flood the body causing physical changes, a monumental reorganization of the brain begins. Weaker connections are trimmed and stronger ones are reinforced. As a result, the brain, particularly the ‘prefrontal cortex’ shrinks by one percent per year during teenage.

A part of the brain called the ‘medial prefrontal cortex’ becomes hyperactive. This is the activity centre of self-evaluation. The brain is beginning to create a sense of self. A teen’s self-consciousness steeps in social settings and peaks at the age of 15. Imagine a new pair of shoes and you are struggling to break into it. By the age of 25 you will get used to it. And gradually it will become your second skin. But teens, alas, will remain socially awkward and hypersensitive.

Another centre called the ‘dorsolateral prefrontal cortex’, which is an agency of impulse control, is still maturing and will be fully developed only at the age of twenty. On the other hand, the pleasure seeking centre, called the ‘nucleus accumbens’, is already developed. To make matters worse, the centre that aids in decision making, called the ‘orbitofrontal cortex’, is as underdeveloped as that of a child’s brain. The last straw on the camel’s back is that the ‘striatum’, the centre that translates motivations into actions, is strongly coupled with the hyperactive ‘medial prefrontal cortex’. All these neural chaos and cacophony make a teen unstable, indecisive and risk-prone. 

Next time we exasperate over the ‘odd’ behaviour of a teenager, let us remember that beneath the behaviour, inside the cave of the cranium, intense and inevitable neural metamorphosis is occuring.

(Paraphrased from The Brain by David Eagleman)