Look at the scope of the topic used by the authors of the article. For example, you might be thinking about writing a paper that reviews all the interpersonal literature about nonverbal communication.
If you are not sure about what categories exist within the topic of nonverbal communication, you could look at titles and abstracts of twenty or thirty articles that surfaced when you searched for nonverbal communication.
In those articles, you may begin to see patterns--ten articles about eye contact, three articles about touch, etc.
This kind of detective work is critical to good research.
When you decide to focus on that single area, you may feel disappointed to leave out all the many other interesting areas you considered.