Answer:
When developing a fixed mindset during middle childhood, the self-efficacy level of a child will not develop, and they will have the potential to stay on the same level of productivity throughout childhood and bring the same mindset to adult life.
It is important to develop a growth mindset since very young in order to make it easier when this mindset is in a solid foundation and is being applied in the adult life. With a growth mindset in adult life, the person is more productive, flexible and has potential to grow in productivity and self-efficacy.
In sum: develop a fixed mindset during childhood, it will be harder to change during adulthood vs develop a growth mindset during childhood, it will be easier to keep it during adulthood and improve even more.
Explanation: