Why we’re letting Americans vote, marry, and drink far too young

And this trend of turning a blind eye to the reality of age laws continues today, even as science has proved that their foundation — that at 18 we can assume people are sufficiently developed to make reasoned decisions and offer informed consent — is wrong. The prefrontal cortex, the part of our brains that aids in decision-making, is not done developing until 25, which means we’re giving people the right to make decisions based on the expectation of full cognitive maturity seven years too early — and in some cases many more than that.

But this advancement in scientific understanding has done little to dislodge the hodgepodge of state laws granting rights, privileges and responsibilities at ages ranging from 8 to 21. For example, 33 states currently have no minimum age of criminal responsibility. In other words, in most states a 5-year-old or a 10-year-old (or even a baby) could be legally charged as an adult if a judge so desired. For a federal crime, the legal age of criminal responsibility is 11 years old. While in many states a 12-year-old cannot be legally left at home alone, such a child could be charged as an adult with a federal crime.

And race plays a big factor in who experiences these out-of-date standards: It is Latino, Native American and African American youths who are disproportionately tried as adults, while white youths receive much lighter sentences.