Final answer:
Grace trying to mimic her mother's silly faces is an example of observational learning, which shows that even infants can learn by watching and imitating others.
Step-by-step explanation:
Rebecca making silly faces at Grace, her five-month-old baby girl, and Grace attempting to imitate those faces, illustrates the power of observational learning in developmental psychology. Observational learning involves watching and imitating the behavior of others, as evidenced by Grace's attempts to replicate her mother's expressions. This type of learning occurs when an individual, in this case, a baby, observes someone else performing a behavior and then tries to imitate that behavior themselves. The situation with Grace and Rebecca exemplifies how even infants are capable of learning behaviors through the simple act of watching, which is a fundamental component of human learning and development.