The aim of the introduction to a research paper
The introduction to a research paper orients your reader to the context of your study. It gives the reader just enough background to understand why you’re doing the work. Many journals require authors to keep introductions quite brief, limiting them to only 500 words or fewer in some cases. Even if a journal does not limit the length of the introduction, you should still try to be as concise as possible.
What to include in the introduction to a research paper
The introduction to a research paper should follow the chain of reasoning that led to the question or hypothesis your study addresses. You do not need to start in the deep history of the research field or cover its background entirely.
The best approach is to list for yourself the key findings that led you to perform this study and identify the key publications that cover those findings. If you re-create as briefly as possible the chain of discovery that led to your work, the introduction to the research paper is doing what it should.
Once you have that story in hand, you can write the complete introduction.
The order of elements in the introduction to a research paper
You should open with a paragraph that sets the stage. In this paragraph, you will usually mention the specific topic—whether it’s a disease, a biological pathway, a chemical synthesis, an economics area—and why research in this area should interest the reader. The opening will be the most general part of the introduction. As you write the rest, you will narrow down your information, like an inverted pyramid, until you reach your research question at the end.
As an example of a general opening sentence for an introduction:
“Multiple sclerosis (MS) affects 1 million adults in the United States, but the disease process for the least common form, primary progressive MS (PPMS), remains unclear.”
You can then cite the chain of key findings that led you to your research question. As an example (all of this material is fictional):
“Myelin destruction is the unifying process in MS, but in PPMS, this destruction focuses in the spinal cord, rather than the brain. A key immunological pathway involving the protein NP3 acts only in the spinal cord, with no evidence of expression in the brain white matter. In addition, increases in NP3 expression have been identified among people with PPMS compared to unaffected individuals.”
After walking your reader to this point, you can now tell the reader what you’re doing as the next step in this PPMS-related research:
“We have identified a receptor that binds NP3 in vitro. To evaluate its effects in vivo, we have created a knockout MS mouse model that exclusively does not express this receptor in the spinal cord in adulthood. Our hypothesis was that these animals, unlike their typical MS mouse model counterparts, will show no of the usual motor signs of MS.”
You have now reached the end of the introduction to your research paper. For each statement you make in establishing the context and chain of key findings that led you to your question, you will need to provide the most relevant and, where possible, most recent reference or references.
Some journals expect that authors will give a brief statement of their takeaway findings at the end of the introduction. Other journals do not want others to include such a statement and to hold results-related information for the results and discussions sections of the research paper. You can view recently published papers from your target journal to see what the editors seem to expect. If you do need to include a key takeaway at the end of your introduction, here is an example:
“Our results show that these knockout animals that stop expressing this NP3 receptor in adulthood show a substantial delay in developing MS-related motor signs compared to the unmodified MS model animals. These findings suggest that the NP3 receptor contributes to but does not fully explain the disease process in PPMS.”
Dos and don’ts for the introduction to a research paper
- Do start with a broad, brief statement about the subject of your study, follow the chain of key findings, and close with a statement of your study aim, question, and/or hypothesis.
- Do follow the “inverted pyramid” shape in laying out your story for the introduction, beginning with a general context and narrowing the story until it ends at your pointed research question.
- Don’t write an introduction to a research paper that is a recitation of seemingly disconnected information and ends with the reader having no idea what your research question is or why you’re asking it.
- Do give your reader the information they need to understand why you’re doing this study.
- Do keep details to a minimum.
- Don’t overload the reader with data or information.
- Do use the most recent references you can find, if possible.
- Do cite reviews for readers who might want a deeper look at the background for your study, if the journal allows authors to do so.
- Don’t use the introduction to a research paper as a place to write a mini-review of your own.
- Do use language that people from other scientific disciplines can understand.
- Do keep your paragraphs relatively brief, breaking up your chain of key findings into easy-to-follow chunks, narrowing your story toward your study question.
- Don’t write the introduction as one long block paragraph unless the journal specifically requires it (some journals, especially those that require quite short introductions, will specify that the introduction be a single paragraph).