A thorough literature review is vital before you start a project. The main goal of a literature review is to determine what research has been conducted, how it was conducted, and what knowledge gaps still exist.
A study that has already been conducted is rarely worth repeating, except in special situations such as a studying a unique technique, population, or setting. Therefore, you must familiarize yourself with the literature before deciding how you can make a novel contribution to your field.
Where to start
A literature evaluation begins with a search of databases of indexed articles. Many researchers often use Google Scholar; But please be aware that there are no strict requirements for being indexed in this database. Accordingly, Google Scholar indexes reputable journals as well as less reputable sources, including non-peer reviewed sources and predatory (fraudulent) journals. Please use Google Scholar with caution.
We recommend that you begin with broadly focused academic databases like Scopus or Web of Science, as they will find relevant articles across disciplines. But you should also search databases for your field, such as PubMed, PsycINFO, or SciFinder. Some specialized examples are Reaxys, which chemists use to locate compounds and reactions. Another example is the Cochrane Library, which clinical researchers use to find clinical trials and systematic reviews.
Be familiar with how different databases work, because they can often assist you in finding additional articles. For example, if you open an abstract in PubMed, it will list the titles of articles that have cited that article (thus leading to more up-to-date research about the topic), as well as review articles and other related articles. As discussed earlier, review articles are another excellent source of relevant studies for your literature review. Finally, you should make a habit of visiting websites of reputable journals in your field and sign up for customized e-Alerts and e-mailed Tables of Contents (e-TOCs) to stay up-to-date.
Because each database uses different algorithms to find articles, you should search for articles in two or more databases—we recommend using one broad-focused database and at least one field-specific database.
Articles in journals of some disciplines such as linguistics, but also in engineering and computing, often begin with a short Introductions section that presents the author’s field, topic, and hypothesis. What then follows is a literature critique or literature review, which assesses the state of current research and theories, and presents an argument from that assessment. It reviews current published work, its logical strengths and weaknesses, and the evidence for and against it.
The topic of research must clearly fit into the context of the literature, and key variables that feature in the research should be explained and defined in the literature critique. Although disciplines in the humanities and social sciences allow authors to quote the literature (within quotation marks or, for larger stretches of text, as an indented block quote, and always with a citation), such reproduction should not be too extensive. Material quoted should form a coherent academic argument.
A professional journal will also expect a literature critique to identify flaws or gaps in the literature, and point the way toward alternative theoretical models and/or the kind of evidence that would be needed to support them. A literature critique may include supportive evidence from text or data analysis.
Identifying gaps in the knowledge
A literature review will help you identify knowledge gaps. It can also help you to refine your research question. But you should also review the literature after you have started your study. This is because other researchers might have done a study like yours. Check the literature — especially in the month, and week, that you submit your research manuscript.
Even if an area of study already seems researched and key findings have been copied many times, there are still chances to find new research gaps. You could ask yourself these questions:
- Have past results been replicated using different study designs?
- How different are the methods used?
- Is there still opportunity to produce a new technology?
Especially in a newer field, there may still be methods that have not yet been used. Changing and evolving technology stimulates innovation in new study designs.
Also, you could ask about the setting or population. Have the same results been found in different populations? Often, researchers do studies using a convenience sample. Such studies may not generalize to the population. You could design a study that shows if published results can be replicated with new samples or subjects. But keep in mind that such studies often lack novelty. They may be more difficult to publish.
Review the Discussion sections of published articles for research ideas. Authors will often discuss future directions that can be useful in identifying current gaps in the field. Authors will also discuss their limitations, which can either serve as a basis of technological innovation or as a warning to researchers planning to do similar research.