Every morning, four-year-old Marta watches her mother put on a suit, pack a lunch, and place her lunch and briefcase by the front door before leaving for work. One day, Marta wakes up, puts on one of her mother's suits, packs snacks in a lunch bag, and places the lunch bag and a backpack by the front door. She then runs to her mother and says, "I'm ready for work!" Marta's behavior is best explained by which of the following theories?