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The brain - old and new

Thank you for your support in this journey so far. The response has been far more than anticipated and it seems that decision-making is a topic important to many.

This is the second blog in a series of blogs about how to see decision-making as a precious resource rather than something we can apply at all times. The previous blog (The constraints of decision-making ( covered the concept of the limits of bandwidth, time and energy. Our brain faces many of the same limitations that computers do.

This week I cover how the brain is thought to have evolved and an introduction to how it works.

The evolution of the brain

Our brain can be viewed as having two parts- a flexible part of the brain (new brain) and a hardwired brain (old brain). To understand it, it helps to first understand its humble beginnings. It is a truly fascinating journey.

The first living creatures, which were merely single cells, already had some forms of sensing and responding, for example, moving towards food.

As organisms increased in size and developed into structures that had many cells, there was a benefit in cells being able to communicate with each other, as the cells started to specialize. It is here that we identify the first and most important use of our brain - survival. The quicker and more effectively cells communicated with each other, the better the whole organism responded to its environment.

As organisms got more complex, electrical and chemical signals helped different parts of the body to communicate with each other. The cells that conveyed these signals over time developed into neurons. Neurons are an efficient way of using a mixture of chemical and electrical methods to send messages around the body and a convenient building block for more complex systems.

The old brain

Networks of neutrons were the next advance. At first they were evenly distributed over the body but later became more concentrated. The first ‘brain-like’ structure of concentrated neurons appeared in a worm-like creature, which was one of our less glamorous ancestors. It is worth stressing here that for sensory development to be beneficial, they had to improve survival and reproduction.

At the next stage of evolution our fish ancestor developed a part of our brain that helps us respond to fearful situations. This part of the brain called the amygdala is still a part of our brain now and will refer to it as our old brain. Many of the basic functions like reward systems, movement and fear were present in our ancestors 500 million years ago. That, to me, is truly staggering.

The new brain

The 'new brain' was an additional structure that started to develop in our ancestor species that had flexibility. Rather than being as hard-wired as the old brain, the new brain gave its owners flexibility and a capacity to respond in a more nuanced way. The new brain also enhanced the sense of smell, touch and ability to work collaboratively.

The key difference between humans and other apes, is humans have a much larger new brain - 70% of our brain volume is the new brain. The new brain gives us capacity to manage relationships better and use more complex signals to communicate with one another. It is here that we have to give a shout out to Yuval Hariri, who calls humans 'storytelling monkeys' in the book Sapiens. There is a lot of truth to this. The large new brain has enabled humans to communicate abstract concepts like love and friendship not known to be present in any other species.

So through understanding the evolution of our brain, I hope it is now clear that we have two key parts of our brains that have conflicting agendas. When we resist reaching for a delicious cake, our old brain is identifying high nutrition food whereas our new brain is reminding us of our low carb diet!

The old brain can ensure we continue to breathe, digest and have protective reflexes, whereas the new brain can help us learn language, play music, do puzzles - the new brain is allowing to read this blog.

How does the new brain work?

The leading theory of how the new brain works (proposed by Jeff Hawkins) is thinking of the new brain as a forecasting model. It takes in data, and develops models of the world from it. The key is that many neurons are making predictions in parallel, and those neurons which closely predicts what actually happens become more electrically active i.e. the new brain trials lots of models of the world and then select ones that seem to have the best predictive ability. Relevant to last week's blog about energy, the more a model seems to be predicting the world correctly, the more the brain's electrical activity centres around only that series of neurons and the remaining brain activity is low. Brain activity picks up a lot, if something outside of the prediction happens as the brain goes back to trialling different models of the world.

So how is this all relevant to decision-making? Here are three take-aways I want to leave you with before we pick it up next week:

1) We have an old and a new brain. Each has a different solution to challenges we face. You might regret a decision made impulsively that could have had a better outcome if it had been better thought through.

2) Our new brain is constantly making models of the world, but often with very few data points. We will sometimes think we understand something that we really don't.

3) It is less effort for us to ignore data that disagrees with our model of the world. Considering new data means we have to rethink things and that means more electrical activity and hence more mental effort.

Next blog in a week's time will cover 2) and decision-making errors that result from not realising we do not have the full picture.

Links for further reading on these topics:

A Thousand brains by Jeff Hawkins

The evolution of the brain


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