How to write a great introduction: filling the gaps

The introduction to a journal article serves many purposes. First, the author introduces the reader to the basic problem to be addressed in the manuscript. If the article deals with a molecular mechanism that is involved in gastric cancer, for example, the introduction may open with a general overview of gastric cancer, including prevalence and incidence.

In a well-written introduction, the author then leads the reader down into the finer details of the subject matter. Continuing with the gastric cancer example, if the manuscript deals with a mechanism that is important in the generation of resistance to chemotherapeutic agents, the author may introduce the reader to the general problem of chemoresistance, finally homing in on the particular type of agent that will be the focus of the study.

The subsequent paragraphs provide an overview of the current state of knowledge, providing in-text citations that illustrate the important contributions to the field leading up to the time of the writing of the current manuscript.

The overall purpose of the introduction to this point is to lay out the current stage of knowledge in the field. This is where we come to the most important point in the introduction: identification of the gaps in the current state of knowledge.

The limits of knowledge

By definition, science is a body of knowledge. The reason to publish any academic article is to add to the fund of knowledge of the subject. Articles in scholarly journals should do just this, even if they are systematic reviews and meta-analyses of previously published works. To make worthwhile contributions, it is essential that the author identify the limits of knowledge in a particular field. Returning to the gastric cancer example, it may be the case that no investigator working in the field has studied the mechanisms of resistance to boneymaronab (a fictional monoclonal antibody). The climax of a well-written paragraph would be a statement such as “To the best of our knowledge, the mechanisms of resistance to boneymaronab in gastric cancer are unknown.”

Mind the Gap

The overall purpose of the introduction to this point is to lay out the current stage of knowledge in the field.

Epistemological humility

Notice that the climactic sentence began with the phrase “to the best of our knowledge.” This type of epistemological humility is not required, but it is nevertheless a good idea. In fact, it may be the case that a reader has already published a mechanistic study of boneymaronab resistance in gastric cancer that the author was not aware of. Even if this were not the case, it does not hurt to hedge one’s bets, or to be humble.

The punchline

Now that the author has established the gaps in knowledge in the field, the time has come to describe how the study that follows will fill those gaps. There are several methods for doing this, some better than others.

One method to avoid is to essentially reproduce the sentence describing the gaps, with modifications. If the “gaps” sentence is “To the best of our knowledge, the mechanisms of resistance to boneymaronab in gastric cancer are unknown,” it is not advisable to follow up with a “fill-the-gaps” sentence that reads “Therefore, we studied the mechanisms of resistance to boneymaronab in gastric cancer.”

Instead, tell the reader what you actually did in the study. For example, “Therefore, we studied the role of micro RNA-fake on the WXYZ regulation of boneymaronab degradation in cultured gastric cancer cells.”

No spoilers!

A common mistake that many authors make at this point is that they divulge the conclusions of the study too soon. For example, they may write “We found that miRNA-fake stimulates WXYZ activity to increase boneymaronab degradation in gastric cancer cell lines.” Recall that this is an introduction, not an abstract or discussion. Presumably, the reader already knows the conclusion, having read the abstract.

Like a cliff-hanger in a good television mystery series, the end of the introduction should leave the reader wanting to know more. In particular, how did you actually go about filling the gaps in the state of knowledge that you have so expertly laid out?

If done correctly, the reader will keep those gaps in the knowledge base in mind while reading your manuscript, focusing on how each method and result aims to fill those gaps, right up until the finishing touches in your conclusion.

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