On social media, a claim regularly resurfaces: the human brain would only reach maturity at age 25. While this simplified idea is often shared, it actually obscures the nuance of current neuroscientific knowledge.
This belief in a developmental stop at 25 stems from brain imaging work in the 1990s and 2000s. This research, published in journals like
Nature, revealed a decrease in grey matter volume during adolescence, linked to a pruning of seldom-used neural connections. As the data often stopped around age 20, the age of 25 later became established in the collective imagination as a convenient threshold, although scientists never spoke of a strict limit.
Illustration image Pixabay
More recent work, based on the examination of thousands of brain images, shows that the organ continues to transform well beyond that age. Thus, a study published in 2025 in
Nature Communications presents a new analysis. It highlighted a phase described as "adolescent" spanning from age 9 to 32, during which the brain architecture remains particularly malleable.
Throughout this extended period, the brain implements two complementary mechanisms. It first specializes certain areas for specific functions, such as organizing related thoughts. At the same time, it establishes fast links between these regions to ensure efficient information exchange. It is only around the age of thirty that this organization settles into a configuration representative of adulthood.
The efficiency of this internal network, assessed by a parameter called "small worldness", constitutes a relevant indicator of brain age. It can be likened to a transport network that becomes more efficient, with fewer transfers needed to connect two destinations. The brain optimizes its circuits in this way to process increasingly complex data until around age 32, before consolidating the most frequently used pathways.
This persistent plasticity represents an opportunity to actively shape one's brain abilities. Practices such as intense physical exercise, acquiring new languages, or playing strategy games can support this adaptability. Conversely, prolonged stress can slow it down. Therefore, there is no ideal date of brain maturity, but rather a construction site extending over several decades, where our experiences directly influence the ultimate architecture of our mind.
Grey matter and white matter: the two components of the developing brain
The brain organ is usually described according to two broad categories of tissues that transform differently. Grey matter, formed by the cell bodies of neurons, constitutes the primary site of information processing. During childhood and adolescence, its volume increases and then slightly decreases during a phenomenon of synaptic pruning, where infrequently used neural connections are eliminated to increase efficiency.
White matter, on the other hand, consists of long axons wrapped in myelin, an insulating substance. These axons act like cables ensuring rapid transmission between different grey matter areas. While grey matter reorganizes relatively early, white matter sees its quality and arrangement gradually improve over a much longer period, into early advanced adulthood.
This progressive maturation of white matter is fundamental. It speeds up communication between distant brain regions, which facilitates the coordination of multiple thoughts, rapid decision-making, and emotion management. Development is therefore not uniform: while some structures become operational early, the wiring that interconnects them is refined for many years.
Grasping this duality helps understand why cognitive abilities change over such a long period. The overall performance of the brain depends less on the number of neurons than on the quality of the links that unite them, a network that continues to be fine-tuned well beyond one's twenties.