Science Says This Is The Age You Actually Become An Adult

Marking the passage of time with birthday parties and milestone celebrations is a simple way to track chronological development. But in reality, the dividing lines between childhood, adolescence, and adulthood are much less clear.

When it comes to legal status, at 16 many find a set of car keys in their hands, and at 18 (the age of legal adulthood in the US) teens can vote, sue someone, run for office, buy certain firearms, join the military, or get married (via Dallas Morning News). At 21, you can legally buy and consume alcohol and tobacco products.

If the ages set for some of these privileges and responsibilities seem arbitrary, it's because, to some extent, they are. How can an 18-year-old be mature enough for the commitment of marriage, but not mature enough to drink a beer? The question of what actually makes someone an adult, and at what age that magical stage is actually attained, is complicated and full of variables. And really, should adulthood be measured by age, or by responsibility?

For years, there has been a basic consensus among scientists that most brains do not fully develop until around age 25, and that, largely because of this, young people tend to use less restraint and discipline than older people (via The New York Times). This understanding has had major legal implications, especially when it comes to criminal justice.

Is being an "adult" more about responsibility, or age?

Now, more recent research by brain scientists has pushed the date for full brain development back even further, into the 30s (via BBC). Cambridge University Professor Peter Jones says, "What we're really saying is that to have a definition of when you move from childhood to adulthood looks increasingly absurd. It's a much more nuanced transition that takes place over three decades."

The transition to adulthood is one that researchers have had a hard time marking with any sort of scientific accuracy. The age at which people self-report "feeling" like adults varies wildly, and in most cases coincides with taking on a number of major life responsibilities, like getting a mortgage or having children (via BBC).

Laurence Steinberg, professor of psychology at Temple University, says "Chronological age is not a particularly good indicator [of maturity], but it's something we need to do for practical purposes. ... What's really important is that the transition into adult roles is taking longer and longer" (via The Atlantic).