Last week, I went to work with 1.3 litre of milk. In Canada, you can buy milk in packages of 4 litres, the 4 litres being divided into 3 smaller bags each containing 1.3 litres of milk. To give you an idea of the size, if you’re not familiar with Canada’s bags of milk, I’ve copied a picture below.

The milk I brought to work wasn’t for drinking or my tea or a cooking activity. I was bringing it in as a psychoeducation tool. The brain, you see, weighs 3 pounds – the same as a 1.3 litre bag of milk.  After years of practicing psychiatry, I have learned that you must sometimes make your point as concretely as possible. This is especially true when your patients are adolescents and their brain is still developing.

To illustrate the human brain even more completely, I also tell patients and their parents that the brain is about the size of 2 fists held together, each fist representing half of the brain. I read this in Frances Jensen’s The Teenage Brain. This reference reminds teens and parents that the brain is made up of two halves. Even though most people know this, the image can be helpful.

I find that these images – of two fists held together or the three pound weight of a bag of milk – really do help people to understand the vulnerability of this small organ to all that can happen to it. Events like a bang on the head or a concussion, or the use of alcohol and drugs, have one impact one your 130 pound body, and quite another on your 3 pound brain.

The brain doesn’t change much in size or weight between age 16 and 24, but what does change are the number of connections among the different parts of the brain. It is the development of connections that helps teens to make better decisions and to learn and consolidate executive function. I have an illustration from that really shows this much better than I could ever describe.

Every teen and every parent would benefit from knowing this information. How many times have you heard a teen say, “I wish I had thought about what was happening before I reacted?”

How often have you heard a parent say, “Why on earth did Sarah do that? She knows better.”

Finally, now we understand Mark Twain’s famous line:

“When I was a boy of fourteen, my father was so ignorant I could hardly stand to have the old man around. But when I got to be twenty-one, I was astonished at how much the old man had learned in seven years.”



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