Consistency of verb tense helps ensure smooth expression in your writing. The practice of the discipline for which you write typically determines which verb tenses to use in various parts of a scientific document. In general, however, the following guidelines may help you know when to use past and present tense. If you have questions about tense or other writing concerns specific to your discipline, check with your adviser.
Use Past Tense…
To describe your methodology and report your results. At the time you are writing your report, thesis, dissertation or article, you have already completed your study, so you should use past tense in your methodology section to record what you did, and in your results section to report what you found.
- We hypothesized that adults would remember more items than children.
- We extracted tannins from the leaves by bringing them to a boil in 50% methanol.
- In experiment 2, response varied.
When referring to the work of previous researchers. When citing previous research in your article, use past tense. Whatever a previous researcher said, did or wrote happened at some specific, definite time in the past and is not still being done. Results that were relevant only in the past or to a particular study and have not yet been generally accepted as fact also should be expressed in past tense:
|"Smith (2008) reported that adult respondents in his study remembered 30 percent more than children."||Smith’s study was completed in the past and his finding was specific to that particular study.|
|"Previous research showed that children confuse the source of their memories more often than adults (Lindsey et al., 1991)."||The research was conducted in the past, but the finding is now a widely accepted fact.|
To describe a fact, law or finding that is no longer considered valid and relevant.
|"Nineteenth-century physicians held that women got migraines because they were 'the weaker sex,' but current research shows that the causes of migraine are unrelated to gender."||Note the shift here from past tense (discredited belief) to present (current belief).|
Use Present Tense. . .
To express findings that continue to be true. Use present tense to express general truths or facts or conclusions supported by research results that are unlikely to change—in other words, something that is believed to be always true.
|"Genetic information is encoded in the sequence of nucleotides on DNA."||Note also that no source citation is needed here since it is a widely known and well-accepted fact.|
|"Galileo asserted that the earth revolves around the sun."||The asserting took place in the past, but the earth is still revolving around the sun.|
1) “Singer (1982) stated that sexual dimorphism in body size is common among butterflies.”
2) "Sexual dimorphism in body size is common among butterflies (Singer 1982)."
|Here you use past tense to indicate what Singer reported (sentence one), but present tense to indicate a research result that is unlikely to change (sentence two).|
|"We chose Vietnam for this study because it has a long coastline."||
Use past tense to indicate what you did (chose Vietnam), but present tense to indicate you assume that the length of Vietnam's coastline is unlikely to change.
|"We used cornmeal to feed the fingerlings because it provides high nutritional content at a relatively low cost."||Past tense reflects what you did (used cornmeal), but present tense indicates that neither the nutritional content nor the cost of cornmeal is likely to change.|
To refer to the article, thesis or dissertation itself.
|"Table 3 shows that the main cause of weight increase was nutritional value of the feed."||Table 3 will always show this; it is now a fact that is unlikely to change, and will be true whenever anyone reads this sentence, so use present tense.|
To discuss your findings and present your conclusions.
|"Weight increased as the nutritional value of feed increased. These results suggest that feeds higher in nutritional value contribute to greater weight gain in livestock."||Use past tense to indicate what you found [weight increased], but use present tense to suggest what the result implies.|
Publication Manual of the American Psychological Association, 5th Ed. The Comprehensive Guide to Writing in the Health Sciences, University of Toronto.