Additional variables - may often add nuance or an external explanation for a relationship. – is a variable that explains how two variables are related in different ways for different people or different situations. – explains why two variables may be related based an explanation that is internal.

Rick is a toddler with an easy temperament and active nature. people are often seen stopping to talk to him in supermarkets and parks where his mother takes him in the evenings because he smiles willingly at other children and adults. this aspect of rick’s behavior most likely reflects a(n) active genotype–environment interaction suppressive genotype-environment interaction passive genotype–environment interaction evocative genotype–environment interaction