A junior colleague and I were discussing a paper she had written, when she apologetically asked:
Would it be too obscene if I cited this paper in my upcoming presentation?
Modesty, I suppose, would dictate that you don’t talk much about your accomplishments, and I can see how fear of appearing vain might hinder one from self-citing. On the other hand, I would argue that it is, in principle, the author’s responsibility to direct the readers’ attention to all the relevant research that has been previously published, even if one happens to have been involved in its publication.
In the paragraphs that follow, I explain why self-citation may be appropriate, and follow up with a couple of cautionary comments.
To begin with, self-citation may be justified on account of the cumulative nature of scientific work. This means that, as long as your research agenda is coherent, your new research will build on what you have learnt (and published) previously. In such cases, citing your older publications would be a helpful way of contextualising the new research. It would also be a useful opportunity to point out how the new publication adds to the academic record, lest you create the impression that you are salami-slicing your research. Moreover, in view of increased sensitivity regarding self-plagiarism, it is best that you cite, rather than repeat, relevant information that you have used in the past.
Secondly, self-citations may be necessary in order to demonstrate how your thinking has evolved. When working on a research topic over a long period of time, you are likely to develop new, more refined understandings, at which point you may want to critically re-evaluate your previous publications. Failure to do so might create confusion among readers, who may not be able to appreciate subtle conceptual shifts between older and newer publications.
All that said, there are a couple of things you need to be cautious about when citing your own work: Firstly, self-citations should add value for the readers. This means that you should not cite your own papers just for the sake of boosting your ego, or for the more insidious purpose of increasing your bibliometric rankings (the number of times an academic has been cited is sometimes used as an indirect measure of research quality). Excessive self-citation risks annoying reviewers, who may justifiably ask for revisions. As a rule of thumb, I would advise against more than one self-citation per paper.
Furthermore, when writing for a journal that practices anonymous (‘blind’) peer-review, you should take care that your self-citations do not give away your identity. Journals will often have specific instructions on how to deal with self-citation (e.g., you may be asked to replace your name with “Author”, or to remove first-person pronouns). Some journals, by the way, have policies limiting the use of self-citation, so make sure you read the instructions to the authors very carefully.
To recap: provided you do not indulge in gratuitous self-citing, references to your previous publications are perfectly legitimate, and may in some cases be necessary.