Scientists often struggle to write paper introductions. Introductions are often short (in some journals 1-2 paragraphs) and when we edit manuscripts, we commonly see requests from writers to cut them down to size. We find that introductions are most likely to be too long when you try to write the Introduction first, before you have completed your analysis. It’s easier to keep an introduction short and to the point when you’ve clarified your paper’s message.
A good introduction takes your reader from a familiar starting point and guides them through 4 (or 5) stages:
- sparking interest in the general problem or issue of concern
- explaining the state of current research about that issue
- demonstrating a knowledge gap or problem that must be solved
- offering your hypotheses (optional)
- summarizing your solution to the problem.
Stage 1: Start where your reader will start. You will write a different opening sentence and paragraph if you are writing for a generalist journal than for a specialized journal. The goal of this section is to make clear both your topic and its significance. For example, if you tested a treatment for a disease, make sure your audience knows how many people have the disease, what populations it harms, etc.
Stage 2: Few research projects start in a vacuum. Describe the research that inspired your project, and especially focus on describing and explaining the significance of studies to which you will compare your results in the discussion section. (This is why we suggest writing your discussion section first. Only then will you know which studies you must first mention in the introduction.)
Stage 3: Point out shortcomings or limitations in existing research. These are the reasons that support your decision to conduct this particular study. Your problem statement should be a clear, memorable sentence framed as simply as possible.
Stage 4: Many research projects do not begin with hypotheses and that’s fine. But if you do start with a hypothesis, make clear what you expect to find.
Stage 5: Write a short summary of your goals and method and specify your main outcomes (what you will measure, how you will measure it, what type of analysis you will perform). This is usually a paragraph that begins something like, “Our goal was to…” Often this is a single sentence, and the last sentence of the introduction. You can think of it as the topic sentence for your whole methods section.
The hardest part of writing an introduction is keeping out all the facts and ideas that don’t belong in the paper you’re writing. You know so much about your subject that it’s impossible to share all of it, but it’s hard to limit yourself. It’s very tempting to write about your topic, when you should really be focused on preparing people to read and understand the specific arguments you will make in your discussion.
This is why we recommend waiting to write the introduction until you’ve finished your analysis, formulated your message, and written the discussion. Only then can you be certain which information your reader needs to understand your message.