In your literature review in the Introduction Section, you usually need to refer to studies that happened in the past. Therefore, using the simple past tense is the obvious choice. However, skilled authors tend not to use past tense for most of their literature review, but instead use it only occasionally when they wish to refer to a specific study or make a particular inference about a specific study.
What is Simple Past Tense?
The simple past tense usually involves using the author’s name and the past tense version of the reporting verb. The final two sentences of Paragraph Version 2 are written in the past tense (the terms in bold indicate the instances of simple past tense):
However, Orchard et al. (1972) argued that eating mangos too often could have negative effects on overall health, and Vintner (1987) said the same of grapes. Emdee et al. (2007) even suggested that overconsumption of these fruits can lead to the development of intolerances.
What does Simple Past Tense imply?
In the sentence above, the author probably feels that these findings are once-off and may not be generally applicable: only these particular authors (e.g. Orchard et al.) have shown these findings (e.g. that eating mangos too often is bad for you) in this particular study (Orchard et al. 1972), and therefore there is only this one data point to support this conclusion. In other words, there is a subtle implication, when simple past tense is used as in the above sentence, that these findings are not, or may not be, true in general.
To make this implication even stronger, authors sometimes refer specifically to the specific study in the sentence, and put the findings in simple past tense as well (e.g. “eating mangos too often had negative effects on overall health”). This carries a stronger implication that these findings were only shown to be true in that specific case, and that in other circumstances the findings may well be different. Compare the following sentences:
- Founder et al. (1927) showed that summers are longer than winters.
- Founder et al. (1927) showed that summers were longer than winters.
- In their study of 1924-1926, Founder et al. showed that summers were longer than winters (Founder et al. 1927).
While in sentence 1 the author might be suggesting that this is a finding that may not be widely applicable because it has only been obtained once, in sentences 2 and 3 the author seems to be suggesting not only that this finding has only been obtained once, but also that it may only have been the case in this 1927 study. Sentence 3 is a little more specific about the precise timing of the finding, implying that perhaps summers were only longer than winters in the years in which Founders et al. collected their data, 1924 to 1926.
Are there other ways to use Simple Past Tense?
Another way in which simple past tense can be used is when using a storytelling approach to write the literature review, or a section of it. A storytelling approach means relating the various findings in the literature review as a series of events in sequence, as if you were telling a story. This is a slightly unusual approach to writing academic literature reviews, but when interspersed with the more common approach it can be used to make a literature review more engaging and interesting to read. Consider the following example:
Smith et al. conducted a two-year field experiment in 2009 and 2010 in rice paddies to learn about the connection between rice production and greenhouse gases emissions (2011). Two years later, this experiment was repeated by Jones and Kingston (2015).
Sentences like these could form part of a story about how our knowledge about the connection between agriculture and greenhouse gas emissions has developed. In this way, simple past tense can be used effectively for a storytelling approach.
Simple past tense can also be used in the part of the Introduction Section that refers to the present study (although simple present tense is more commonly used nowadays). Here is an example:
In this study, we examined the likelihood of developing a food intolerance after eating a range of quantities of mangoes every day. We hypothesized that a daily consumption of two mangoes or more would lead to food intolerances in at least 50% of adults.
What happens if I use Simple Past Tense too much in my Introduction Section?
If you use simple past tense a lot in your Introduction, firstly, the text will sound stilted and rather clumsy to a native speaker. Secondly, it will soon become monotonous and boring to read. Thirdly, it may be taken to imply that you have little faith in all or many of the findings you are reporting. So, to sum up, do use simple past tense in your Introduction Section, but use it mostly for reporting studies that you have little faith in or which represent singular data points that you feel may not be representative in general.