“Kidults” could be a better term for those in their twenties, according to research which suggests that people do not become adults until about 25.
The adolescent desires of sensation-seeking and novelty in the brain increase as individuals leave home and fend for themselves, Beatriz Luna, a psychiatrist the Pittsburgh School of Medicine, believes.
Previously, such desires were thought to peak at 15, but new studies found that they extend far beyond this age.
A key finding is evidence of hyper-activity in a part of the brain known as the striatum, which is stimulated by “rewards” and this continues until the mid-twenties.
It is thought that the typical “adult responsibilities” of holding down a stable job, paying a mortgage and raising a family halt the effects on the brain.
Prof Luna said that the age people crossed the threshold of adulthood was “probably closer to 25”.
In teenagers the sensation-seeking part of the brain works together with the “planning centre”, or pre-frontal cortex, to drive curiosity and experimentation.
“Sensation seeking, which is really information seeking, novelty seeking, is evident across species and human societies,” Prof Luna said at the American Association for the Advancement of Science (AAAS) annual meeting in San Jose, California.
“I'm saying this is combining with a brand new shiny car called the pre-frontal cortex. The adolescent is, like, 'Oh, this is great, I can plan', but they're doing it in the service of this heightened sensitivity to motivation,” she added.
The system allows young people to seek out novel situations and not always ask “mummy and daddy”.
Prof Luna is still conducting research to discover how far into adulthood the brain changes continue, but it is possible they may extend into a person’s thirties.
“There are two ways to look at it. I'm a very positive person, I'd like to think the longer you have to specialise the better,” Prof Luna said.
“I guess the implication is that when the environmental demands are those that require you become a responsible adult, meaning you have a lot of responsibilities to take over, that might be signalling the brain to stop a certain type of plasticity because now you really need stability and reliability.
“Having the freedom to play a bit longer in life might be a good thing,” she added.