To beat Trump, we need to know why Americans keep voting for him. Psychologists may have the answer

[Caliman73]

16. Twin Studies strongly suggest that it is BOTH to varying degrees.

Human behavior is one of the hardest things to quantify and categorize because of the factors that influence it. If you have significant damage to specific parts of the brain, that may inhibit your ability to develop certain traits or to control your impulses. Stress (in many forms) also has a profound effect on neurochemical transmission and absorption.

Hormones also play a large part in whether or how certain structures within the brain develop.

What I say is that we do not have the technology to detect and intervene within the brain right now so the best thing that we can do as a species is to create an environment where human flourishing is maximized and deal with those "odd situations" as needed. As of right now, the environment for most people on earth is very stressful and that is a result of CHOICES by people with power and wealth who do not want to share some of theirs to ensure that everyone has enough to have a decent life.