Distinctions are awarded to those students who go beyond what they have been taught. This has two main components. The first is reading widely. The second, equally important part is thinking critically and applying what they have learnt in some modules to the material in others. In particular, you get outstanding marks if you do not just cite research but briefly describe the comments and methods used in the research. “Research by X shows” is a very weak statement. Lots of research shows nothing at all because it is badly designed or conducted.
You should apply what you have learned about methods and think sceptically about all research you read. When you review an area say which research is designed well and why this is so, and which results have been replicated, and so on. It is perfectly acceptable to say about an area where little research has been carried out that little is known because satisfactory studies have not been carried out. Get into the habit of using a cautious critical vocabulary: “So and so seems to be the case” or “research so far suggests” or “unfortunately most studies in this area have failed to….”.