Answer: Differential susceptibility.
Explanation:
The concept of differential susceptibility can be defined as the concept which states that the people development and emotions are affected differentially susceptible to the qualities or experiences of the environment.
The serotonin transporter gene is not transferred to the children whose mother is suffering from depression during the time of pregnancy and they act to be immature.
Whereas, the mother who are happy have a mature child so the mother's should be kept happy at the time of pregnancy.