Elaine is very sociable and outgoing. She enjoys speaking in public and chooses to teach large lecture classes. She often meets friends for lunch and is active in fundraising for the local children's hospital. Her spouse Jon is predisposed to shyness and often engages in solitary or small group activities such as biking, going to movies with friends, or reading. He works in a small office setting as a budget analyst. This illustrates which of Scarr's assertion of how genes interact with the environment?