Answer:
rule out rival hypotheses using additional research
Explanation:
A rival hypothesis is an explanation of an effect which is not what the researcher first hypothesized. Developmental psychology deals with studying the psychological changes a person goes through in the span of their lifetime. This includes childhood and adulthood.
When a child is being studied for behavioral problems a wrong explanation for the behavior may lead to a remedy that may be in fact harmful for the mental development of the child.
Hence, any rival hypotheses must be ruled out.
