The brain is not fully developed until the early twenties
Robby Starbuck said:
“You don't complete the process of your brain being fully developed. Early twenties is when science and medicine agrees that the brain is fully developed. You can look across all different peer reviewed papers on this. They all universally agree that the brain doesn't finish developing until you're in your early 20s.”
The idea that the prefrontal cortex matures into the mid-twenties is genuinely present in neuroscience literature and is widely cited in public debate about adolescent decision-making, so it sounds like settled science.
Brain development is not a single event with a single finish line: different regions mature at different rates, serving different functions, and the research on prefrontal cortex maturation is specifically about impulse control and risk-taking, not about self-knowledge. Knowing your own gender is not the same cognitive task as deciding whether to jump off a cliff. It is a stable, usually deeply held sense of self that most trans people describe recognising long before adulthood, not a decision reached through an act of daring. Applying one finding from developmental neuroscience to the entirely different question of whether an adolescent can articulate who they are is a category error, and one that does real work, because the same logic would invalidate adolescent consent to cancer treatment, surgery, or contraception, none of which we restrict on these grounds. Every month that a young person with gender dysphoria is told to wait is a month of an unwanted puberty they cannot reverse, and they are paying for a misreading of the science.
What I said at the time:
“What do you mean fully developed? What do you mean by fully developed? I mean, your brain is fully developed when you're born. Much earlier in in utero, your brain is fully developed. So what do you mean?”
Adolescents with gender dysphoria are denied agency over their own healthcare on the basis of a misapplied neuroscience claim, and the same logic would invalidate adolescent consent to any medical treatment.