What is a literature review

The definition in plain words

Imagine explaining to a colleague what is known about a question, who found it out and how, where the data contradict each other and what nobody has tested yet. The written answer is a literature review.

The key word is "critically". A review does not just list works; it appraises them: how convincing the methods are, how the results relate, which limitations the authors admit.

Why it is needed

• To show you know the field and are not repeating what has been done.
• To justify relevance: the review ends with the gap your work closes.
• To choose a method: see which approaches were already applied and with what result.
• To give the reader context for understanding your contribution.
• As a genre of its own: to summarise a field for those entering it.

What a review is not

Not an annotated bibliography, where sources are described one by one without links between them. Not a summary, which retells one work. Not an introduction, which poses the problem, whereas the review shows what is known about it.

A test: remove the surnames and years from the text. Does a coherent argument remain? For a review it does; for a list it does not.

What a review consists of

1. Question and boundaries. What the review is about, which period and which types of work are included.
2. Search method. Where you searched, with which queries, how you screened. In a systematic review this is a detailed protocol; in a narrative review, a paragraph.
3. Main body by theme. Several sections, each with its own claim and a comparison of works.
4. Synthesis. Agreement, contradictions, gaps.
5. Implications for your study. What exactly you will do and why it follows from the review.

How to tell the review is done well

• Every paragraph has a claim supported or challenged by several sources.
• There are recent works, not only decade-old classics.
• Contradictions and their possible causes are named.
• A gap is formulated and leads logically to your work.
• Every reference is checked: it supports exactly what it is attached to.