Answer: Self-concept
Step-by-step explanation:
Self-concept is defined as the believes, characteristics,capabilities and value an individual holds for self.It defines the knowledge a person has about his/her own-self.
According to the situation mentioned in the question, Stephen can persist better self concept as compared with Clint because he had rapid growth than him.This situation induces more self consciousness and self evaluation in Stephen's case than Clint because adolescents tend to focus more on unique attributes through believes.