Puberty: a time of change

1. attention, remodelling work in progress!

Even if puberty is initially characterised primarily by physical changes, at least as many changes take place in the adolescent brain during this developmental phase. This is because the release of sex hormones leads to a fundamental remodelling that initiates the final maturation of various areas of the brain - such as the so-called grey matter in the cerebral cortex. It is formed by nerve cells and synapses - the connections between nerve cells.

During puberty, it's time to declutter: Less-used synapses are reduced, frequently used ones are strengthened.

In early childhood, their number grows rapidly: new synapses are formed with every learning experience a young child has and thus brain structures are linked together. The type, quality and quantity of learning experiences that a child has determine how dense and therefore powerful their neural network is at the start of puberty. During puberty, it is time to declutter: Synapses that are rarely used are reduced, while those that are frequently used are strengthened. This thinning is not a loss, but rather serves to increase brain performance. At the same time, there is an expansion of nerve fibres that transmit information between nerve cells more quickly.

Teenagers have the shortest reaction times

The speed of the brain and thus of thought processes increases many times over, as does the ability to concentrate. Teenagers have the shortest reaction times of all age groups. However, brain maturation during puberty and adolescence is gradual and does not take place simultaneously in all areas of the brain. The prefrontal cortex, which is responsible for impulse control and planning, among other things, is the last to mature.

It is not fully mature until the age of 20 to 25. Until then, adolescents are only able to think rationally to a limited extent and are less able to suppress impulses - such as those from the areas of the brain that evoke emotions and are particularly active during this developmental phase. This explains what makes adolescents so susceptible to emotional outbursts and mood swings.

Adolescents need stronger stimuli than adults to feel a rush or a sense of happiness.

Their tendency towards bravado and risk-taking is also due to remodelling work in the brain: The death of unused synapses temporarily means that fewer stimulating stimuli reach their limbic system - the «reward centre» - where the so-called happiness hormone dopamine is released. This means that adolescents need much stronger stimuli than we do in order to feel a kick or a sense of happiness.

Neuroscience also shows that young people are temporarily less able to read emotions from faces. This means that they are no longer as good at interpreting the feelings of the other person, which makes them more insecure - and sometimes makes them very wrong in their reactions.

2. why puberty starts earlier and earlier

The development of sexual maturity occurs earlier worldwide today. «The start of puberty has shifted forward by four to six years over the past 200 years,» says youth researcher Klaus Hurrelmann . Researchers suspect there are many reasons for this. These include a higher-calorie diet - a prerequisite for reproduction is sufficient fatty tissue - chemicals that enter the body via plastic objects and can have a hormone-like effect there, but also the modern lifestyle with stress, lack of sleep and noise pollution.

Humans in their time as hunter-gatherers were sexually mature much earlier.

However, more and more scientists are also suspecting an evolutionary-biological connection. For example, the New Zealand paediatrician and hormone specialist Peter Gluckman. According to him, humans were sexually mature much earlier in their time as hunters and gatherers - and had their first children at the age of 12 to 14. It was only after people had settled down that they were confronted with a deteriorating nutritional situation in several successive epochs and - for example in the early industrial period - catastrophic living conditions that postponed the onset of sexual maturity.

Oskar Jenni, Co-Head of Developmental Paediatrics at Zurich Children's Hospital, also believes that there is much to suggest that premature puberty is not a first-time phenomenon, «but rather a correction towards the original normal state».

3. when peers take precedence over everything - even at the table

Throwing healthy snacks in the bin or spurning the family meal to eat at the takeaway afterwards: Peers sometimes have a frustrating influence on the eating habits of adolescents. This can also be observed in the animal world, as medical doctor and evolutionary biologist Barbara Natterson-Horowitz writes in her book «Young Savages»: "If you give Norway rats a choice between a tasty food that they like to eat and an unpleasant one that they don't like, they always choose the tasty one.

Rats in puberty ate poison when the others did too

But when pubescent rats were brought together with their peers in a study, their choices changed. The likelihood of the rats abandoning their own taste preferences and copying those of their peers doubled," says Natterson-Horowitz. «This went so far that they ate poison: Even though they had gotten sick from spoilt food in the past, they would eat the poisonous stuff when they saw the others doing it too.»

Information from peers about the immediate environment is often more up-to-date than information from parents.

However, the behaviour of the young rats has a demonstrable ecological reason, says the researcher, «and it could also play a role in humans. Information from peers about the immediate environment is often more up-to-date than information from parents. On well-worn tracks, benefiting from resources, status or traditions, older animal parents may not have noticed the changes in the food ecosystems that the younger animals are closer to - and which affect them far more.»