Most psychologists agree that environment, more than heredity, influences who a person is and what she or he will become

This is True.

A prominent topic of debate in psychology is whether human behavior is influenced by a person's environment or innate hereditary influences. This argument is commonly known as the nature-nurture debate. However, most psychologists support the nurture argument, and believe that while genetics do play a role in behavior, a person's environment plays a significantly larger role in influencing who a person is and what she or he will become.