In formal academic writing, especially theses and journal articles, most text about methods and previous research is written in past tense (e.g., ‘We interviewed 666 people living in metropolitan Melbourne’; ‘Aitken et al studied a sample …’). Nevertheless, in some disciplines (largely in the social sciences) the use of present tense is permissible for describing literature. This can read slightly oddly, especially when referring to long-dead authors (‘Socrates tells us’; ‘Milton writes’), but is fine when it’s consistent. Introduction, discussion and conclusion chapters or sections often use present tense, unless the field is palaeontology, history or another past-focused discipline.
I would opt for present rather than past tense in the following circumstances:
- text relating to the document itself (‘this thesis describes'; ‘the next chapter concentrates on’; ‘these results indicate’)
- references to other published documents/theories/concepts, because they are essentially eternal (‘Einstein’s Theory of Relativity holds that’; ‘Aitken et al’s article shows’; ‘the Act states’)
- text that explicitly describes a phenomenon at a particular point in time (e.g., an evaluation of a public health program) or when there is no expectation of substantial change over time (e.g., a description of a new species)
- text that relates to the implications of research, or conclusions presented as general truths (‘Our research proves that bicycles are more energy-efficient than cars’; The data imply …’)
- when writing about a current and ongoing problem (young Australians’ binge drinking is a serious …’).
There’s a further refinement to point 2, which is that any associated actions or the actual work of the authors themselves (e.g. ‘the report was prepared'; ‘Aitken et al’s research proved that’) as opposed to its result (a document) can be referred to in past tense.