Present perfect tense is more common than simple past tense in a literature review. Present perfect tense is used to describe findings or events that happened in the past but have present consequences. Put another way, present perfect tense should be used when making broad statements about trends or generally accepted knowledge in the field.

What is Present Perfect Tense?

Using present perfect tense usually involves the word “has” or “have” in addition to the past tense version of the reporting verb. Unlike simple past tense, the authors are not referred to directly in the sentence. In addition, temporal adjectives like “recently” and “long considered”, and terms like “much debated” and “extensively studied” usually suggest present perfect tense. This is because these words imply something that did not occur at a specific point in time; rather, they imply trends.

The first two sentences of Paragraph Version 2 are in present perfect tense (bold indicates instances of present perfect tense):

Many studies have shown that eating fruit is good for you (e.g. Browne et al. 1978; Jones et al. 1982; King and Johnson 1984). However, some authors (e.g. Whyte and Greene 1986; Linden et al. 1988) have debated the optimal quantities and proportions of each type of fruit.

Note that these sentences also do not refer directly to the authors who conducted the research, but refer instead to “many studies” and “some authors”, and the names of the authors are given parenthetically as citations.

What does Present Perfect Tense imply?

The implication of these sentences is that these findings have fairly convincingly been shown to be true and are generally widely accepted by the community. In the above sentences, the author seems to feel that it is a fairly well-established fact that eating fruit is good for you, although there has been (in the past) a general debate about the specifics of how much and which types of fruit.

Reporting things for which there is no evidence

Another case in which present perfect tense is usually used is when reporting findings that have not yet been reported in the literature, e.g. Whether apples or pears are better for coronary health has not yet been determined. This is because there is no specific time at which these findings were not reported.

Can you use simple past tense in this situation? Yes — when referring to something specific that some authors did not do at the time of their study, simple past is appropriate, as in 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 gas emissions (2011). However, they did not consider the effects of nitrogenous fertilizers.

So, simple past tense and present perfect tense work very differently when referring to things not done or not found. Take care with these.

What do you do if you are unsure if there is no evidence?

Is simple past tense or present perfect tense appropriate here? Is it even acceptable to admit that you’re unsure in academic writing? Should you not conduct an exhaustive literature review on every aspect of interest in your study? Well, in some cases it can be difficult to be sure whether you have completely covered all the available literature. For example, there may be studies that addressed the question of interest that were published in another language or long ago, and which have also not been discovered by other authors reviewing the topic. In such cases, it is best to use a statement like “To our knowledge, no one has investigated this subject” (present perfect tense) or “To the best of our knowledge, this is the first study to address this issue” (simple present tense).

What happens if I use Present Perfect Tense too much in my Introduction Section?

Present perfect tense is often the most commonly used tense in the Introduction Section, so it is unlikely that you would use it too much. However, it is always a good idea to vary your use of tense a bit, to make the text less monotonous and more engaging. Consider carefully what the implications of the different tenses are, and if you have particular findings or studies that you have somewhat less confidence in, consider presenting them in simple past tense. Conversely, if there are aspects of the established knowledge that you feel very confident about, consider presenting these in simple present tense. Doing this would both relieve the monotony and convey a subtle message to your reader about how much confidence you put in those pieces of information.


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