What is a literature review? As stated earlier, a literature review is not a well-defined genre. Broadly speaking, a literature review is a single publication, or an element of a long publication, where a topic or research question is explored by examining a large body of prior publications relevant to that topic or research question. Literature review publications tend to self-identify as literature reviews by using those words in the title and in the abstract and body of the work. Literature review publications have extensive reference lists and a textual narrative that examines the content of the articles in that reference list. Article databases often allow you to limit results to literature reviews with the click of a button. Literature reviews are numerous and not difficult to locate.
Producing a literature review is a much different process than simply finding one to read. Literature reviews are diverse and dynamic because of the interrelationships among four major rhetorical features: type, form, purpose, and audience. Understanding these features can help you create an efficient research and writing plan, and ultimately craft a compelling final document. You may have observed these features and interrelationships among the review articles you’ve read.
Let’s delve into them.
Literature reviews can be classified into many types based on characteristics like how the source material is found, the reason they are produced, and what they look like in their final form. New types continually evolve—a recent piece of research identified 48 different literature review types!
Let’s look at three fundamental types of published literature reviews:
A narrative literature review is extremely common. You have probably read many literature reviews of this type. You may be tasked to produce a literature review of this type many times in your career. A narrative review uses past published research to tell a story about a topic. In the sciences, a narrative review can bring the reader up to date on an evolving research area, establish the scientific rationale for new research explorations, or provide a history of knowledge on a particular topic. They provide overviews or expert opinions grounded in prior published research on a topic. They are typically produced by a single author, or a small group of authors. A narrative literature review can be educational and informative for subject matter experts or non-experts.
What differentiates a narrative review from other review types is what is missing: a traditional narrative review typically does not follow a standardized method for locating the literature to be reviewed. Traditionally, the assumption is that the reader trusts the expertise of the author, and the review itself doesn't necessarily follow a standard structure. The narrative review does not typically provide detailed information about how the prior research was located, or why some publications were chosen for inclusion over others. Narrative reviews can disclose their method for locating literature, and clarify the authors’ inclusion/exclusion criteria—this is generally helpful to the reader and adds credibility to the author’s words, but it is not a predominant element of the narrative review text. A traditional narrative review usually summarizes the take-home messages of the literature being reviewed, but doesn’t attempt to synthesize quantitative data from multiple studies into a single finding using statistical methods.
It is likely that most literature reviews you will write will be of the narrative review type.
A Systematic Review is a literature review that follows a highly specific protocol from start to finish. A systematic review of the literature intends to answer a specific research question. Instead of conducting laboratory or field research, a comprehensive search of all literature is conducted using a strict and reproducible search protocol that is designed ahead of time and made explicit in detail. The literature being searched can be published or unpublished.
Selection of articles to be included in the review also follows predetermined inclusion and exclusion criteria, and should involve multiple reviewers. A systematic review is actually a research study that uses published literature as data. Systematic reviews should never be undertaken alone, and like other forms of research, require team collaboration and significant time to conduct. The search and selection process for the literature to be reviewed is a significant portion of the systematic review text.
A narrative review can be conducted with methodological transparency, but that transparency alone does not transform it into a systematic review.
A meta-analysis is a sub-type of systematic reviews. A meta-analysis seeks to answer a specific research question using the literature as data. After the rigorous search and selection process is completed, the quantitative data in the individual studies selected for the review is extracted and synthesized (combined) statistically to achieve a result that has higher statistical power than the results of the individual studies. A meta-analysis is a literature review type as well as a research methodology.
The final activity of quantitative synthesis of data from multiple studies is the hallmark characteristic of a meta-analysis and is what transforms a systematic review into a meta-analysis. As a sub-type of systematic reviews, meta-analyses also require comprehensive review of the literature conducted with a specific protocol and adhering to methodological guidelines. Likewise, meta-analyses also investigate a specific research question. The search and selection process, as well as the data analysis, is a significant portion of the published meta-analysis. This type of literature review should also be conducted with a team, and will require significant time.
As you might expect, the form that a literature review takes is closely related to its type. Literature reviews might be stand-alone publications that constitute a research study itself, part of a larger research project and publication, or part of a grant proposal.
Stand-alone reviews are frequently (but not always) themselves scholarly contributions to a field and published in a peer-reviewed journal. They may, either directly or indirectly, seek to move scholarly conversation and professional practice in a particular direction. Stand-alone reviews present the objective, methodology, and findings of their own internal research question. Systematic reviews and meta-analyses are most frequently published as stand-alone reviews.
This may be the form that you are most familiar with. It tends to coincide with the narrative review type. Literature reviews are a requirement for theses and dissertations, as well as for most peer-reviewed articles (when the article is not itself a stand-alone review). In the case of theses and dissertations, the literature review frequently takes the form of a chapter with its own introduction, clearly defined sections, and conclusion. However, it can also take the form of a chapter section, typically as part of the introduction. In peer-reviewed articles, the literature review likewise takes the form of a section within the larger publication, typically as part of the introduction.
The literature review is a common feature in grant proposals as well, though it may not be as obvious as a dissertation chapter titled “Review of the Literature.” Frequently, a brief narrative literature review will be part of the (you guessed it!) “narrative” component of a grant proposal. (Check out Lesson 4 of the Libraries’ micro-course on Grants & Funding for more information about writing grant proposals.) In the case of research grants—like you might write for the NSF, NIH, USDA, or UW-Madison Graduate School—the literature review will most frequently occur within an “introduction” or “background” section of the project narrative.
Any single literature review often serves multiple purposes, so it will be important for you to understand what it is your literature review is meant to do on a few different levels. As you might guess, the purpose(s) of your literature review will strongly depend on its audience, type, and form.
There is one overriding purpose across nearly all literature reviews, however, which is to situate your research within relevant, ongoing conversations.
Imagine, for a moment, what it would feel like to read a scientific article without a narrative literature review incorporated into the text… You would probably have lots of questions! For instance, “What have other people researched in this area? What did they find? What were the implications, and how does this study support or complicate them? What were the limitations of past research, and how is this study’s approach different?”
The same questions could be asked of a dissertation or grant proposal without a literature review, and systematic reviews and meta-analyses simply wouldn’t exist! The most important thing your literature review needs to do is to summarize and synthesize existing research in a way that creates space for a new perspective—your perspective—to enter the conversation.
Depending on its type, form, and audience, your literature review might also seek to:
Especially when a literature review is part of a thesis or dissertation project, one of its purposes may be to demonstrate your deep knowledge of the research area to an audience of specialists. The research project itself serves as a testament to your readiness to enter an industrial or scholarly profession, and the literature review, specifically, testifies to your knowledge of relevant research and your ability to synthesize that research into a coherent narrative.
If your literature review is part of a grant proposal, it will likely need to communicate the broader impact of your research to an audience of non-specialists. Often, that impact will be framed within the context of real-world problems or challenges that your research aims to address. While your research project as a whole might propose changes in professional practice, public policy, or manufacturing products, the literature review can help you to establish the context for that change by providing an overview of what has and has not been done already.
In the case of systematic reviews and meta-analyses, one major purpose must be to contribute new knowledge to the field through the review itself. Remember, these types of reviews are research studies themselves, whereas narrative literature reviews summarize and synthesize other research.
Who will be engaging with your literature review? This element is closely tied to purpose and will impact choices you make while writing. Some audiences may be particularly interested in your literature review due to its type and form. The type and form of your review may also require particular writing conventions.
What type of specialized knowledge or experience does your intended audience likely have? Is it likely that your intended audience has deep knowledge of your discipline and area of expertise? You may be able to avoid explanatory passages in your writing by assuming common knowledge or experiences. If your literature review is likely to challenge a status quo within a research area, you may need to devote more text to justifying the challenge. Also, readers who have specialized knowledge in your same area are likely to also know the literature well. Establishing and disclosing your inclusion/exclusion criteria, even in a narrative literature review, can help you respond to challenges.
For instance, suppose a senior faculty member, your advisor, or a peer-reviewer questions why you included certain publications in your review but did not include specified other articles. You may need to defend your choices, and having clearly defined inclusion/exclusion criteria already established will help you form your response to a challenge.
We are defining a non-specialist as a person whose specialized knowledge is within a different scientific context than yours, or doesn’t run as deeply as yours. If you anticipate that your readership will include persons outside of your specific discipline, you may need to devote space to explaining the concepts and connections you are making so that their significance is readily apparent. For instance, if your literature review is a component of a grant application, the reviewers will likely have deep, specialized knowledge of their own, but not necessarily within your precise research area. It is important to not assume that they will automatically see how your literature review supports your funding need. A non-specialist may also not have a deep knowledge of the literature in your area and, as a critical reader, will want an understanding of your inclusion/exclusion criteria as well.