Question

N the berkeley longitudinal study some years ago, early-maturing boys perceived themselves _____ than did their late-maturing counterparts. when the late-maturing boys were in their thirties, however, they had developed a _____ than the early-maturing boys had.

Answer 1

I believe the answer is:  more positively; stronger sense of identity

 early-maturing boys perceived themselves because they are less likely to met some examples of people that they could look up to in their age group.
And the stronger sense of identity tend to be developed after they socialized with other people and obtain the knowledge of the things that they like and they don't like.