Megan and her friends are in a mall for Christmas shopping. Megan is not in a good mood as she had an argument with her sister in the morning. As they enter a store, they are greeted by an employee dressed as Santa Claus. There is a general feeling of excitement and festivity among her friends and other shoppers in the store. After a while, Megan realizes that she is not upset any more. In fact, she becomes excited about shopping and even finds a lovely scarf for her sister. In the given scenario, Megan's changing mood is an example of _____.