This note is part of an ongoing series intended to ensure that readers focus on your research rather than on phrases that may not sound natural in English. During the manuscript review process, every reviewer has a limit to exposure to awkward wording; if this threshold is exceeded, reviewers tend to shift their focus to language differences and may even refuse to finish reading the manuscript! My goal is to suggest more natural phrases and strategies for communication to keep the focus on your high-quality study.

Let’s first look at some sample content using several different verb tenses:

Fig. 7(a) shows the performance metrics for method 2. We calculated the confidence intervals using Algorithm III, which first evaluates the derivative; if its value exceeds the mean, then the confidence interval will be doubled. The results were satisfactory except for material A, which exhibited anomalous values. In this study, magnetic-field-processed materials have performed unsatisfactorily. We will address this topic more thoroughly in the following section.

In fact, all these verb choices (calculated, evaluates, have performed, will address…) are appropriate—the passage uses the past, present*, present perfect, and future** tenses in a natural way.

(*For convenience, I’ll include the present progressive or continuous tense in the present tense.)

(**Strictly, the English language has only past and present tenses, with all other forms requiring auxiliary terms. What’s called the future tense, for example, comprises the present tense plus a modifying term such as “will.” I’ll ignore this distinction in this note.)

So that’s not the problem. The problem is keeping track of these tenses throughout the paper. For example, do all “if-then” statements use the future tense? When referees or editors find inconsistencies or—even worse—errors in tense, they may begin to think that the research results aren’t being articulated accurately, which is a scenario we wish to avoid.

It’s actually possible to recompose our earlier passage using the present tense throughout:

Fig. 7(a) shows the performance metrics for method 2. We calculate the confidence intervals using Algorithm III, which first evaluates the derivative; if its value exceeds the mean, then we double the confidence interval. The results are satisfactory except for material A, which exhibits anomalous values. We find that magnetic-field-processed materials perform unsatisfactorily. We address this topic more thoroughly in the following section.

This passage expresses the identical meaning but doesn’t require the author (or the reader) to shift between the past, present, and future tenses. Here, no transitions are necessary.

The present tense is tremendously powerful! It implies that something always happens, not that it happened just once. It implies that a process always occurs, that a statement is always true. This sense of permanence is valuable in our academic writing, in which we seek to convey universal truths as revealed by our research.

The present tense is useful for leading the reader through a process that can be repeated at any time

Processes that we’re free to repeat include analytical techniques, algorithms, simulations, and experimental procedures when the testing apparatus and specimens still exist. In this case, readers (and reviewers and editors) can imagine the process occurring as they read the paper or at any point thereafter:

In this procedure, we first calculate the standard deviation and then evaluate the 95% confidence interval.

We choose an adiabatic boundary condition for the left wall.

The cross section of the rear truss remains elliptical with a progressively shrinking primary axis.

We configure the tensile testing apparatus to halt at a strain of 2%.

The present tense is useful for expressing statements of truth in the field—information that existed before the study was conducted

To reduce wordiness, avoid adding phrases such as “It is known that” or “We should note that”; it’s sufficient to express the statement of truth succinctly with references:

Au reacts strongly with a Ti adhesion layer at high temperatures [citation].

Algorithms designed to manage distributed generators typically suffer from low computational efficiency [citation].

Natural language processing models include the bag-of-words model and the skip-gram model [citation].

Tropospheric N₂O diffuses through the tropical tropopause into the stratosphere, whereas tropospheric HF is quickly depleted due to the high chemical activity of fluorine [citation].

The present tense is useful for expressing experimental statements of truth—new universal knowledge established in the course of the study

One can write either that “It was apparent that formulations in this range of composition crystallized between 230°C and 250°C.” or, more simply,

We find that formulations in this range of composition crystallize between 230°C and 250°C.

The past tense sounds more natural, however, when the statement refers to a particular finding unique to the study, rather than a universal truth. I describe this distinction in the list of exceptions below.

The present tense is useful for orienting the reader and referring to other components of the paper (e.g., figures, tables, and other sections)

Example:

Figure 6 displays the von Mises stress arising from condition B

Selected material parameters are shown in Table I.

The data in the figure indicate that the real geometric means are less than 0.3 ppmv at all altitutes.

And there’s no need to use the future tense in “In Section III, we will explain the operation of the thick-film transistor.” After all, who knows whether your reader will even read the sections in order? Just apply the present tense to express this statement of fact:

In Section III, we explain the operation of the thick-film transistor.

So we find that the present tense can be used in a wide variety of contexts in a technical manuscript. However, some caveats and exceptions apply:

Always follow the style guide of the journal of interest

Your journal may have specific requirements for verb tense. Some editors, for example, may prefer to use the past tense for the results in the study, reserving the present tense for results taken from the literature. (Put another way, talk is cheap, and our results don’t qualify as statements of fact until cited by another, objective group.)

I haven’t yet encountered a referee report, however, that complains that “We find that X causes Y.” should read “We found that X caused Y.” Reviewers are much more likely to complain about inconsistent and illogical verb tense choices.

The past tense sounds much more natural when an event is unlikely to be repeated

✖ We record seven prominent seismic events between May 2013 and June 2015.
✔ We recorded seven prominent seismic events between May 2013 and June 2015.

✖ Seven additional patients are incorporated into the study one month after it begins.
✔ Seven additional patients were incorporated into the study one month after it began.

✖ We obtain ambiguous contrast-agent images from 32% of the patients.
✔ We obtained ambiguous contrast-agent images from 32% of the patients.

If such statements make up a sizable part of a certain section, consider constructing the other sentences in the section (or at least the paragraph) to use the past tense as well to avoid switching tenses repeatedly. Let’s look at the following sentences, for example:

In the high-salinity conditions, corrosion progressed through precipitate dissolution.
In high-salinity conditions, corrosion generally progresses through precipitate dissolution.

The first sentence is more appropriate for a summary of observations (in the past tense) regarding one certain experiment; note the helper article “the,” which signals that we’re describing a specific set of conditions—the ones we applied in the experiment.

The second sentence is more appropriate for a comprehensive discussion (in the present tense) of corrosion mechanisms; note the helper adverb “generally,” which signals that we’re describing a broad tendency.

The past tense sounds more natural in a literature review

When we discuss previous research reports, the past tense is safest, if only because the authors may not be alive (and in the long run, no author is still alive) and because it might sound somewhat unnatural to encounter “Newton, in his Principia, explains that…” Furthermore, it would be inappropriate to write that “Lin et al. argues that…” if Lin, having obtained subsequent contradictory results, changed her mind several years ago. Better to write that “Lin et al. concluded that…”

Even in a literature review, however, the present tense is always acceptable to express an enduring truth:

Braer et al. developed a suitable algorithm for cryptographic information transfer between three participants. Their method avoids the need for a subsequent confirmation but increases the computation cost by approximately one order of magnitude.

The present perfect tense is necessary when describing multiple events in the past (e.g., previous studies) or a condition that began in the past and extends to the present day

There’s no substitute for the present perfect tense in certain sentence structures that often arise in the introduction and the literature review:

Two studies have previously been performed to identify the underlying mechanism of anomalous bursts.

China has promulgated three increasingly stringent pollution-control standards since 1995.

The increase in highway construction in Brazil has prompted research on durable and inexpensive concrete formulations.

Note, however, that we could always use the present tense to say

We draw on two previous studies addressing the underlying mechanism of anomalous bursts.

Three independent pollution-control standards apply to any new industrial enterprise in China.

Prompted by the increase in highway construction in Brazil, we seek durable and inexpensive concrete formulations.

The past tense generally (but not always) sounds more natural in a summary

The past tense is a suitable default verb tense for the conclusion section:

In this study, we addressed two conditions…

However, statements of fact are always candidates for the present tense when you wish to emphasize the permanence of your results:

We consistently find, in all reservoir types, that a large percentage of oil-bearing fluid is locked in place unless vibrational techniques are applied.

The future tense is appropriate when discussing circumstances after the paper is published

When editing, I find the future tense to often be unnecessarily used (e.g., “If the counter exceeds the number of elements, then the algorithm will halt.”). The problem isn’t that the future tense isn’t appropriate for an if-then statement—it can be. The problem arises when any verb tense is used inconsistently: does every if-then statement in the paper use the future tense, for example? If not, then an inconsistency exists that could potentially (however mildly) frustrate editors, reviewers, and readers.

It’s just as clear to write

If the counter exceeds the number of elements, then the algorithm halts.

In other words, we’re again expressing a statement of universal truth. In fact, the revision is clearer because “will halt” leaves open the possibility that the algorithm halts ten minutes later by design, for example. Even this condition can be specified using the present tense:

If the counter exceeds the number of elements, then the algorithm halts ten minutes later.

Consider such processes as occurring in a timeless manner: if a certain criterion is satisfied, then the corresponding consequence always occurs.

When the topic is an event that’s expected to occur in the future, the future tense is appropriate. But “will” without explanation can sound presumptuous; perhaps the sentiment can be expressed more objectively.

For example, it’s assertive, perhaps overly so, to say “This derivation will be of use to practitioners in the field of oncology.” It’s more in keeping with the mores of the academic literature to say

We expect this derivation to be of use to practitioners in the field of oncology.

And it’s arguably just as assertive—if not more so—to state

This derivation is intended for practitioners in the field of oncology.

This sentence sounds quite assertive to me.

Furthermore, I suggest that readers would prefer “This trend will predominate in the class-A recycling market until 2030.” be replaced with

Consensus is that this trend will predominate in the class-B recycling market until 2030 [list of citations].

or

We expect this trend to hold in the class-B recycling market until 2030 based on predictions by [list of citations].

In brief, it’s worth considering whether a sentence in the future tense can be more clearly expressed in the present tense.

A final note

The previous neural network techniques have been ineffective in this context. In this work, we present an improved neural network that provides superior results by…

Instead of saying “We implemented an experimental procedure to evaluate the carbon content. The reservoir volume is 1 L, …,” we might write

We implemented an experimental procedure to evaluate the carbon content. In this procedure, the reservoir volume is 1 L, …

Instead of saying “We recorded the settlement in Village A from 2008 to 2012. The sensor depth is 2 m…,” we might write

We recorded the settlement in Village A from 2008 to 2012 using the following protocol: (1) Set the sensor depth to 2 m…

The common element is a transition element to guide the reader from what occurred once to what always occurs.

Above all, be consistent throughout the manuscript, as guided by these distinctions. Perceptibly or imperceptibly, a paper with consistent and logical verb tenses tends to read more smoothly and allows the reader to focus on the right aspect: your research results.

About the author: John M. Maloney received his Ph.D. in 2012 in the area of biological cell chemomechanics from MIT’s Department of Materials Science and Engineering, where he most recently held a full-time appointment as Research Scientist. He has published research reports in Nature Biotechnology and Nature Materials and holds 10 patents in the area of microfabrication and medical device design. As a freelance technical editor, certified by the Board of Editors in the Life Sciences, he has edited thousands of manuscripts, focusing on helping non-native English speakers articulate their research results with sophistication and technical precision.