Self-plagiarism is a complex and sometimes misunderstood issue and one that students and supervisors may struggle to navigate. There is the actual issue of plagiarism which would be considered research misconduct whether you plagiarised yourself or others. However as theses are published online and as students are actively encouraged to publish their research, there are issues of copyright to consider. Violation of copyright would also be considered misconduct.
The guidance below is broadly based and in no way should be taken as legal advice. You may find that you need to seek more specialist advice depending on your individual circumstances. The links on the right as well as under the 'Additional Resources' section will guide you to additional material which should provide a starting point.
There are broader issues that are considered self-plagiarism as well as poor research practice with regard to publication, such as duplicate, redundant or segmented publication. These are explored more fully in some of the resources provided. However, there are several different issues that apply specifically to PGR students and the submission of their thesis.
Self-Plagiarism is defined as a type of plagiarism in which the writer republishes a work in its entirety or reuses portions of a previously written text while authoring a new work. Writers often maintain that because they are the authors, they can use the work again as they wish; they can’t really plagiarize themselves because they are not taking any words or ideas from someone else. But while the discussion continues on whether self-plagiarism is possible, the ethical issue of self-plagiarism is significant, especially because self-plagiarism can infringe upon a publisher’s copyright. Traditional definitions of plagiarism do not account for self-plagiarism, so writers may be unaware of the ethics and laws involved in reusing or repurposing texts.
Authors can quote from portions of other works with proper citations, but large portions of text, even quoted and cited can infringe on copyright and would not fall under copyright exceptions or “fair use” guidelines. The amount of text one can borrow under “fair use” is not specified, but the Chicago Manual of Style (2010) gives as a “rule of thumb, one should never quote more than a few contiguous paragraphs or stanzas at a time or let the quotations, even scattered, begin to overshadow the quoter’s own material” (pg. 146).
Ithenticate. The Ethics of Self-Plagiarism. (White Paper)http://www.ithenticate.com/resources/papers/ethics-of-self-plagiarism. Viewed 06/08/2015.
Whereas plagiarism involves the presentation of others’ ideas, text, data, images, etc., as the products of our own creation, self-plagiarism, occurs when we decide to reuse in whole or in part our own previously disseminated ideas, text, data, etc without any indication of their prior dissemination. Perhaps the most commonly-known form of self-plagiarism is duplicate publication, but other forms exist and include redundant publication, augmented publication, also known as meat extender, and segmented publication, also known as salami, piecemeal, or fragmented publication. The key feature in all forms of self-plagiarism is the presence of significant overlap between publications and, most importantly, the absence of a clear indication as to the relationship between the various duplicates or related papers.
Miguel Roig. Plagiarism and self-plagiarism: What every author should know. Biochemia Medica 2010;20(3):295-300. http://dx.doi.org/10.11613/BM.2010.037
Plagiarism is not permitted
Plagiarism is not permitted. This refers both to re-using any material including your own without appropriate attribution / referencing and to re-using previsouly assessed material in later assessments. For example, you may not pull material directly out of your Master's dissertation and re-use this in your PhD thesis. There are nuances to this as with anything - you may re-use short sections of material if it is properly acknowledged. 'Short sections' may be a matter of opinion and depend as much on the nature of the work itself as on the actual length of the excerpt.
Students should refer to the University Calendar for more information, in particular the section on 'University Fees and General Information for Students' which contains the University's Plagiarism Statement. Specifically:
Plagiarism is defined as the submission or presentation of work, in any form, which is not one's own, without acknowledgement of the sources. Plagiarism includes inappropriate collaboration with others. Special cases of plagiarism can arise from a student using his or her own previous work (termed auto-plagiarism or self-plagiarism). Self-plagiarism includes using work that has already been submitted for assessment at this University or for any other academic award.
Copyright issues: within your thesis
Students need to be aware of copyright issues if re-using their own previously published material within their theses. If you have published your research, for example in a journal article, you will have come to some sort of copyright arrangement (even if you are not aware of this) with the publisher of that article. You would need to seek appropriate permission for re-using significant portions of material if your thesis is to be published online / placed in an online repository.
If you use small amounts of material (text, images or otherwise) you may likely acknowledge these as you would any other source that you would reference without seeking specific permission. However, what would be deemed a 'small amount' or substantial part can vary depending on a number of factors and you should seek clarification if there is any doubt. Decriptors such as 'small amount', significant portion' or 'substantial part' are not defined legal terms and would be open to interpretation by examining committees, publishers or even courts of law.
If you are not able to get permission from a publisher or other copyright holder, you will need to consider other options than publishing your full thesis online. Many publishers accept that theses are published online and will grant permission. However, permission must be sought. The Library, via Enlighten: Theses, provides some information about including third party copyright material in your thesis and about restricting access to your thesis.
There are differing views as to whether it is appropriate (beyond the issue of copyright) to include entire pieces of work, such as journal articles, within your thesis as a chapter or chapters. You are strongly encouraged to discuss this with your supervisor and to seek advice from your Graduate School if this is relevant to you. In some subject areas it may be encouraged while in others there is the view that including one or several pieces of work in their entirety does not contribute to the sustained and logical argument that is required of a thesis. This is not specifically prohibited in the University regulations - rather, it would be the call of the examination panel as to whether as to whether this was appropriate.
Copyright issues: publishing after your thesis is submitted
Once you have submitted your thesis, you may want to publish the results of your research in various ways. Before making your thesis available online, you should consider whether it is appropriate to publish/ deposit your thesis online and/or whether a period of embargo or restricted access would be best. Publishers are aware that students must generally publish their theses online so if you have a publication in the works or an intended outlet for a proposed publication, you should check that publisher's and/or that specific journal's guidance on this. When submitting your article, you should make sure that the publisher is aware that some material will be from / based on your thesis. It is up to the journal to make a call as what they feel is acceptable.
An interesting article from the UCL Library in their series on 'E-theses Best Practice Summaries' refers to the 'Impact on Future Publication': Brown, J.; Sadler, K.; (2010) Impact on future publication. (E-theses Best Practice Summaries ). UCL (University College London)
Influencing the Deposit of Electronic Theses in UK HE (useful best practice summaries downloadable from this page)