The Introduction has two functions. One is to awaken the reader's interest. The other is to be informative enough to prepare readers, whether or not they are specialists in your field, to understand the paper.
To awaken interest, an Introduction should be direct and to the point, and it should be as short as possible consistent with clarity and informativeness. In addition, it should be written in a readable style (see Chaps. 1 and 2).
To be informative, an Introduction should follow the guidelines given below.
The Introduction section of a paper presents the first step in the story line. What the first step is depends on the type of research. In a hypothesis-testing paper, the first step is the question. In a descriptive paper, it is the message—for example, the key features of a new structure. In a methods paper, it is the new or improved method, material, or apparatus. How this first step is presented for the various types of papers is explained below.
CONTENT FOR HYPOTHESIS-TESTING PAPERS
For a hypothesis-testing paper, what the reader needs to know from the Introduction is what the question of the study was and where it came from, that is, why the author is asking this question. The question, which is the most important statement in the Introduction, is stated either as a question or as a hypothesis. The story of where the question came from is composed of what is known or believed about the topic and what is still unknown or problematic.
Material and Animal or Population
The Introduction should also name the material (molecule, cell line, tissue, organ) studied and the organism from which it came, or the animal or human population studied. When necessary, this statement can be expanded into a statement of the experimental approach taken to answer the question.
No Answer, Results, or Implications
The answer to the question should not be included in the Introduction. Similarly, results should not be included in the Introduction, nor should implications. The purpose of the Introduction is to lead into the paper. Answers, results, and implications sound like the end of the abstract. They close off rather than leading in.
Retrospective vs. Prospective Study Design
If a study was retrospective, that is, if a question was asked after the data were gathered, the fact that the study was retrospective must be stated in the Introduction. For example, "In this retrospective study, we asked whether…." If a study was prospective, that is, if the experiments were designed and the data were gathered specifically to answer the question, that fact does not need to be ...