Answers to those puzzles

We started with some examples of observations about how the mind works that are quite surprising. They come about because of the particular way the brain works – and you could probably design an effective machine-learning device that didn’t have any of these features. Let’s go back to the questions, in case you didn’t spot the answers.

Why can I forget what the capital of Hungary is, but not that I’m afraid of spiders?

The two types of knowledge are stored in different memory systems. The amygdala in the limbic system, which detects threats, doesn’t forget. In the cortex, which stores vocabulary, knowledge fades without use: partly, unused connections are co-opted by other knowledge; partly unused connections are no longer maintained.

Why do I find I have learnt things better after a night’s sleep?

One of the roles of sleep is to consolidate the brain connectivity changes that underlie learning, making the stored skill/knowledge more stable and effective. Sleep also plays a role in extracting the key themes from learning, and integrating it with previous knowledge.

I get 7 out of 10 in a test – why am I delighted if I was expecting to get 5, dispirited if I was expecting to get 9? A 7 is just a 7, isn’t it?

The brain’s reward system is driven by whether its expectations of rewards are met. It gets excited when rewards are bigger than expected, upset when rewards are smaller than expected. It’s not driven by the objective level of performance.

Why does my mind go blank when I’m stressed in an exam?

The limbic system interacts with the frontal cortex, so that emotional states can influence goals and how thinking is controlled. The threat of the examination situation causes the release of hormones that put the system in fight-flight-freeze mode, with both physical and cognitive effects. The frontal cortex is involved in retrieving and activating the right knowledge for the current situation. When it is hijacked by the limbic system (under the guise of an emergency threat situation: run!), it is unable to activate the knowledge to begin answering questions.

While we’re here, interestingly, stress can even interfere with highly practised skills, in a process we know as ‘choking’ – such as when professional sportsmen flunk under pressure. Self-consciousness makes the cognitive control system monitor the performance of automatic motor pathways and affect their smooth functioning. It’s like trying to dance whilst checking that your feet are making the right moves. Always goes wrong.

Why as a teenager did I start doing risky things to impress my friends?

The hormone changes in puberty influence the motivation and reward system, shifting the priorities from the family to peers, and towards taking risks to achieve status with peers. Long-term planning – and learning sensible risks to take – involves both experience and development of prefrontal cortex, which continues into early adulthood.

Why do I learn a new language so much more easily when I’m 5 than when I’m 50?

The brain reduces its plasticity by throwing away resources for changing connectivity from middle childhood onwards. The brain focuses on strengthening connections of the skills it has acquired. This trimming of resources for plasticity with age mainly affects sensory and motor systems: hearing sounds in a new language and articulating them.


The quest continues for a deeper understanding of how the brain works. As we understand more, we are led to ways to improve outcomes. Here are but a few lessons suggested in this essay: progressive de-sensitisation therapy for phobias; practice for maintaining declarative knowledge; naps / optimising sleep duration for consolidation of learning; stress reduction techniques / graduated exposure to stress situations to improve confidence for exam performance; virtual life-lesson experience for teenagers; early exposure to sounds of different languages for young children; perceptual training in foreign language speech sounds for adults.

How the brain works impacts society and individuals on many levels – in school, at home, how we treat people with cognitive decline, how to realise the potential of young people. This essay focused on what we do know. There is much we still do not, and much to gain from further scientific investigation.