Thalia's two-year-old brother Dean watches her whenever she brushes her teeth. One night, Thalia gave Dean a toothbrush and he imitates her actions. Which theory explains how Dean learned these behaviors from his sister?

The answer is observational learning.

Explanation:

Observational learning is an approach which implies observing and imitating different behaviours. This is especially common for children, who reproduce the actions of different models such as parents, teachers and friends. However, adults can also learn by observation: for example, a musician who observes his teacher in order to acquire a technique is also engaging in observational learning.