The human brain has two different ways of processing and evaluating, depending on whether we are thinking about things we can attain easily, or things that will require us to make more of an effort. Easily attainable things include everything that is a result of our work, that has been given to us as a gift, or that we have stumbled upon by chance. Things that require more effort, on the other hand, are outside our physical reach, such as the sky, forests, buildings, or anything we see if we look up. The authors call these two systems ‘the realm of up’, meaning what we achieve by making calculations, taking action, and putting in an effort, and ‘the realm of down’, which is what we are able to possess more easily.
The brain uses different pathways to manage these two systems: everything that is easy for us to possess is regulated by a series of neurotransmitters, which make us feel satisfied and fulfilled for what we already have. Everything else relies on a single molecule, which controls our desire for what we do not possess yet, and for what is harder to obtain. Wanting to travel in space, to become famous, or to achieve a challenging goal all depend on a molecule called dopamine, which was discovered in 1957 by researcher Katheleen Montagu at Runwell Hospital, near London. Dopamine fuels our desires, and drives us to pursue them, even a great sacrifice. Only 0.0005% of brain cells produce this molecule, yet it determines human behaviour more than any other molecule in our body.