Sometimes, journal editors make comments like “You should use XXX tense in your Introduction Section.” What they actually mean, though, is that “Where the rules of English grammar permit the author to choose from various acceptable verb tenses, this journal prefers the XXX tense, although of course tense should be varied, as is natural when communicating in English.”
Uni-edit often helps authors to understand that the journal editor’s comment should not be taken so literally. Here is an example of what can happen if the author assumes that the journal editor means they should use only the one tense they have indicated.
Author’s original work:
Smith et al. (2003) showed that grapes contained high levels of Vitamin A, and Gardner and Plum (2002) found that they had high levels of Vitamin B. Barber and White (2004) discovered that grapes were rich in potassium, but Grey et al. obtained contrasting results in 2006. Browning (2007) argued that grapes were nevertheless an excellent source of many essential nutrients, although Holmes (2006) showed that they sometimes also contained trace quantities of some toxic compounds, such as arsenic.
Journal editor tells author to use present tense in the Introduction Section and so the author changes too many verbs to present tense:
Grapes contain high levels of Vitamin A (Smith et al. 2003) and high levels of Vitamin B (Gardner and Plum 2002). Grapes are rich in potassium (Barber and White 2004), although another study shows that this is not the case (Grey et al. 2006). Grapes are nevertheless an excellent source of many essential nutrients (Browning 2007), although Holmes (2006) argues that they sometimes also contain trace quantities of some toxic compounds, such as arsenic.
What the journal editor actually wants to read is something more like this:
Grapes have been shown to contain high levels of both Vitamin A (Smith et al. 2003) and B (Gardner and Plum 2002). There is some debate about the levels of potassium they contain, with Barber and White (2004) stating that they are rich in this nutrient and Grey et al. (2006) claiming the opposite. Browning 2007 has nevertheless argued that grapes are an excellent source of many essential nutrients, even though Holmes (2006) had previously shown that they can contain trace quantities of some toxic compounds, such as arsenic.
Can you identify how many different tenses are used in the third (last) version above? In spite of this mix of tenses, the overall impression is that the present tense is being used, and therefore that these findings and debates are current and ongoing. The only exception is Holmes’ 2006 finding, which definitely happened before Browning published her paper in 2007.