There are two key factors at play - temperament and reinforcement.

Parents may over-emphasize temperament and over-value personality. We do it all of the time. "That's just his personality." Strong-willed individuals may require more work. Defiance may require more work. Thus, shaping and reinforcement for that child's individual needs requires something different.

See Dr Dan’s new book: https://www.amazon.com/dp/1935576062/?tag=medrounpublic-20