Human brains reach adulthood around age 32.

In the majority of countries, including the United States and United Kingdom, “adulthood” is often said to begin at 18, when people gain certain rights and privileges such as the ability to vote or enter legally binding contracts. But neuroscientifically speaking, the true age of adulthood is one that most people let pass by without any fanfare. 

In 2025, scientists at the University of Cambridge published a study in which they determined the brain goes through five stages of aging — and, on average, the “adult” stage begins around age 32. According to the research, which studied the brains of nearly 4,000 people between the ages of 0 and 90, the human brain has four “turning points” over a lifetime, which correspond to major changes in its neural wiring. Those changes happen around ages 9, 32, 66, and 83, and divide the lifespan into five brain eras: childhood, adolescence, adulthood, early aging, and late aging.

In the first three years of life, human brains form more than a million neural connections per second.

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Babies continuously take in a huge amount of information while learning everything they can about themselves and their environments. After the rapid expansion of the first few years, the brain goes through a pruning process in which some connections are strengthened and others are weakened.

Adulthood is by far the longest of the identified eras, lasting roughly three decades. During that time, the brain is much more stable than in previous eras, without any major changes in its size or physical wiring. There’s also a plateau in intelligence and personality, which don’t go through the transformations often seen in younger people “discovering” themselves and making new neural associations between themselves and the world around them. 

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