It's ALL about the neurotransmitters (and their receptors and sensitivity, but you get the point)
There is literally NO free will
Everything we like, hate, whether we are talkative or shy, happy or sad, excited or bored, what we lik to do and what we don't like to do, the choices we make, it's all 100% controlled by neurotransmitters
There is nothing what "we" are, we are quite passive observers obedient to the chemical reactions in our body, we do what they tell us, we cannot really change anything about it
Semi-legit. Monks and shit do prove that you can influence your neurotransmitters by concentrating hard enough or entering meditative states, though it takes an enormous amount of training, willpower, and time.
Behaviorism is kinda legit too. You can definitely condition people to react to things in specific ways, much like you can with a dog. The environment has a strong effect on neurotransmitters, but we have pretty limited control over that as well.