Structural differences in the brain can lock you into behaviors you can’t control. Take stroke for example—the resulting brain damage can prevent you from speaking. Or with autism, you may flap your hands even if your teacher tells you to stop. That’s because your body needs the flapping to compensate for a deficit in your proprioceptive system. Another structural difference involves the thickness of your brain connections. We all have a coating called myelin that insulates our neural pathways. It builds up with repetition, which helps us form habits and muscle memory. But some people have too much or too little myelination. The problem is that unless you have a traumatic brain injury or degenerative disease, you’re unlikely to ever have a picture taken of your brain. Someone has observed your behaviors and diagnose you based on what they can see, not on what’s happening in your brain. That’s why behavioral rewards and punishments don’t work for everyone. Not only is it ineffective, but it beats down the spirit and the will to keep trying.