July 18, 2013

Weekly Language Usage Tips: Tenses in scientific writing

Posted in tenses in manuscripts at 9:31 am by dlseltzer

A reader writes:

What is your preference regarding the use of present or past tense in a methods section?  It is, of course, all in the past (“We assumed a normal distribution for ….”) but sometimes it seems quite awkward to have everything in the past tense:

“The efficacy of a particular drug is represented by its ability to decrease viral load under perfect adherence. Our baseline assumption is that efficacy of new drugs (the viral load decrement at perfect adherence) is equal to the average of viral load decrements observed by drugs in the same class as the new drug, under scenarios of near-perfect adherence. In our base case analysis, we assume that the toxicity of new drugs was similar to the toxicity level of existing drugs within that category. However, in sensitivity analysis we explore scenarios in which the efficacy and toxicity of pipeline drugs are different from existing drugs.”

“The efficacy of a particular drug was represented by its ability to decrease viral load under perfect adherence. Our baseline assumption was that efficacy of new drugs (the viral load decrement at perfect adherence) was equal to the average of viral load decrements observed by drugs in the same class as the new drug, under scenarios of near-perfect adherence. In our base case analysis, we assumed that the toxicity of new drugs was similar to the toxicity level of existing drugs within that category. However, in sensitivity analysis we explored scenarios in which the efficacy and toxicity of pipeline drugs were different from existing drugs.”

 To me, the present tenses “sounds better” because many of those things remain true even after they are done. “The efficacy is represented” seems more correct that “The efficacy was represented,” because, it is, in fact, still represented that way….and the was implies to me that it isn’t any longer….

 Any thoughts?

This is what I wrote back:

I would put those elements that happened in the past in the past tense, and those elements that are still true—like your efficacy is—in the present. This is how I would write it:

The efficacy of a particular drug is represented by its ability to decrease viral load under perfect adherence. Our baseline assumption was that efficacy of new drugs (the viral load decrement at perfect adherence) would be equal to the average of viral load decrements observed by drugs in the same class as the new drug, under scenarios of near-perfect adherence. In our base case analysis, we assumed that the toxicity of new drugs was similar to the toxicity level of existing drugs within that category. However, in sensitivity analysis we explored scenarios in which the efficacy and toxicity of pipeline drugs were different from existing drugs.

The writer was under the mistaken impression that you can’t mix tenses in our scientific writing. You can. But you have to be deliberate about it though. The reader is correct; putting the first sentence in the past tense doesn’t make sense when you are talking about something that is true now.

The methods section is usually presented in the past tense because it describes something that has already occurred, but in the reader’s case, he is also making a general statement of fact. So as I said, put in the past what was in the past, and put in the present those ideas that remain true today.

1 Comment »

  1. WendyShad said,

    It can be more confusing in the Literature Review Section, since you’re describing other researchers’ work, which uses a mixture of present and past tenses per se. But the same principle still applies, I think.


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