Teenagers are more selfish than adults because they use a different part of their brain to make decisions compared to adults, new research suggests.

Previous work has shown that when children reach puberty, there is an increase in connections between nerves in the brain. This occurs particularly in the area involved in decision-making and awareness of other people’s feelings, called the "mentalising network".

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Blakemore found that teenagers rely on the rear part of the mentalising network to make their decisions, an area of the brain called the superior temporal sulcus. In contrast, adults use the front part, called the prefrontal cortex.

The superior temporal sulcus is involved in processing very basic behavioural actions, whereas the prefrontal cortex is involved in more complex functions such as processing how decisions affect others. So the research implies that "teenagers are less able to understand the consequences of their actions", says Blakemore.

Link.

This helps explain a lot of those "what was I thinking?" moments I invariably have when I recall being a teenager.