Paula was feeling sad, so she decided to go to a comedy club. After being around happy people for an hour, Paula left the club feeling much better. This is an example of:

The answer is mood linkage.

Explanation:

Mood linkage occurs when a person "absorbs" the mood in their current environment. For example, when attending a meeting with friends, it's likely that people will feel amused simply because the environment is fun. This can happen the other way around, too: negative environments might result in a bad mood.

The concept of mood linkage has been studied in relation to the workplace: a comfortable work environment results in more productive workers.

answer; expert witness;

answer; epigenetics;