Question

Early developmentalists tended to focus their attention on __________, often to the exclusion of other parts of the life span.

Answer 1

I believe the answer is: Childhood and preschool years

Childhood and preschool years are the age where it is the easiest for the scientist to make the observation on. (it is very unlikely for people in teenage/adolescents to willingly put themselves in the position where they must be observed by others from close proximity)