According to the text, how long has the scientific study of human development existed?

A clearly defined group used to compare an individual child's test score against is called a:

a. reference group b. comparative group c. standard group d. norm group

Relationships are more likely to persist when lovers

a. have a personality that is different from their partner's. b. base their relationship on passion. c. realistically appraise their partner's strengths and weaknesses. d. idealize their partner.