The danger of any theory that states what a person can or cannot do according to age, gender, race or other variables is two-fold. 1. The individual intending to learn a skill or knowledge, discovering that she is not supposed to be capable, limits her expectations and ends up living down to those expectations and therefore not achieving her potential. 2. The person teaching such an individual, believing in these expectations, gears his teaching toward them consciously or subconsciously, and creates the expected outcome, or even perceives an outcome that is not there. It is a tragedy if an individual wishing to achieve something, ends up not achieving it simply because he won't try, or is undermined in the attempt, because of a theory about his potential. Even if generally true, there are always exceptions.