Psychologist: Birth-order effects, the alleged effects of when one was born relative to the births of siblings, have not been detected in studies of adult personality that use standard personality tests. However, they have been detected in birth-order studies that are based on parents' and siblings' reports of the subjects' personalities. All of these birth-order studies, taken together, show that birth order has no lasting effect on personality; instead, birth order affects merely how a sibling' s behavior is perceived. Which one of the following is an assumption required by the psychologist's argument?
A: Parents' and siblings' perceptions of a person's personality tend not to change between that person's early childhood and adulthood.
B: Parents and siblings have accurate perceptions of the behavior patterns of other family members.
C: Standard personality tests have detected significant birth-order effects in some studies of young children's personalities.
D: Standard personality tests will detect at least some birth-order effects on personality, if those effects exist.
Choose A, B, C or D as your solution.
D