age-maturity discrepancy 

An inappropriate gap between perceived maturity level in comparison with age.

Little Johnny had a large age-maturity discrepancy. His biological age was 13 but had the maturity level of the average 6 year old.

A large polar intelligence matrix in conjunction with an age maturity discrepancy existed between Sarah and Joe. They simply couldn't get along.

age-maturity discrepancy by Ontological June 25, 2018