Active or Passive Voice?

Should the active voice or the passive voice be used in scientific writing? The old school sides with the passive voice, claiming it is more objective because it preserves anonymity. Current recommendations, however, are that the active voice be preferred.

First, a little review: The active voice follows the mantra of subject, verb, object, such as in the sentence “The dog bit me.” The dog is the subject (doing the action), the verb is “to bite,” and I am unfortunately the object receiving the action. The passive voice is when you turn the object of the action into the subject of the sentence: “I was bit by the dog.” Here are a few more comparative examples

Active voice: The hurricane destroyed the house.

Passive voice: The house was destroyed by the hurricane.

Active voice: The students weighed the water.

Passive voice: The water was weighed by the students.

Active voice: I opened the store.

Passive voice: The store was opened.

Note that the passive voice requires more words than the active voice to convey the same information and that it conceals who or what does the action. The wordiness of the passive voice contributes to its lack of clarity, but the biggest problem with the passive voice is that the subject of the sentence can be left out, as in the last example. This can lead to serious confusion, which is not good in a scientific paper.

In scientific writing, concealing the grammatical subject of the sentence may or may not be desired. If you are describing an experimental setup, it is not necessary to say which student built the laser – it suffices to say the laser was built. Thus, in this case, the passive voice is warranted.

However, when presenting and interpreting results, it is important to know who is advancing any given opinion. For example, it is common to see papers that start with “The xyz phenomenon was studied…” or that end with “it was concluded that the theory is valid.” These passive-voice clauses do not tell the reader who studied the phenomenon or who concluded that the theory is valid. It could be that the scientific community studied this phenomenon or that the scientific community concluded that the theory is valid. Or it could be the authors who studied the phenomenon and made the conclusion. The confusion increases when more passive-voice sentences are strung together, making it very confusing for the reader to decipher who is doing what. The result is a paper that is opaque and easily forgotten (yes—active voice leads to better retention, see future blog post).

Another argument that appears in favor of using the passive voice is that it renders the research impersonal and thereby more objective. By removing the human element from the article, it is argued, the focus will fall on the scientific merit of the work. However, this goal can and should be done with the active voice. It suffices to make the data or the scientific results the subject of the sentence, as in the following example:

Passive voice: It was found that the quantum effects dominate.

Active voice: The data reveal that the quantum effects dominate.

By making the data the subject of the second sentence, the goal of objectivity is achieved without using the passive voice.

Here are a few excerpts from style guides to further bolster the case for the active voice:

(1) Excerpt from Robert A. Day (1998) How to Write and Publish a Scientific Paper, pp. 209–210

Let us now talk about voice. In any type of writing, the active voice is usually more precise and less wordy than is the passive voice. (This is not always true; if it were, we would have an Eleventh Commandment: “The passive voice should never be used.”) Why, then, do scientists insist on using the passive voice? Perhaps this bad habit is the result of the erroneous idea that it is somehow impolite to use first-person pronouns. As a result, the scientist typically uses such verbose (and imprecise) statements as “It was found that” in preference to the short, unambiguous “I found.”

I herewith ask all young scientists to renounce the false modesty of previous generations of scientists. Do not be afraid to name the agent of the action in a sentence, even when it is “I” or “we.” Once you get into the habit of saying “I found,” you will also find that you have a tendency to write “S. aureus produced lactate” rather than “Lactate was produced by S. aureus.” (Note that the “active” statement is in three words; the passive requires five.)

You can avoid the passive voice by saying “The authors found” instead of “it was found.” Compared with the simple “we,” however, “the authors” is pretentious, verbose, and imprecise (which authors?).

(2) Excerpt from Ann M. Penrose and Steven B. Katz (2004) Writing in the Sciences, 2nd ed., p. 51

[T]he concrete information in the methods section is usually presented in the simple past tense, either active voice (“We collected water samples every three days”) or passive (“Water samples were collected ...”). Although the “scientific passive” has a long and venerable tradition, it is often easier and more direct to write in active voice, which is the mode preferred by many journal editors in the interests of brevity and clarity. The editors of the Journal of Heredity, for example, directly inform contributors that “first-person active voice is preferable to the impersonal passive voice” (Heredity 2002).

On the other hand, it is observed in the American Institute of Physics Style Manual (AIP 1990) that “the passive is often the most natural way to give prominence to the essential facts” (p 14). The AIP editors offer as illustration the sentence “Air was admitted to the chamber,” in which it is not important to know who turned the valve (p. 14–15). The AIP does recommend shifting to active voice where necessary to avoid confusion or awkwardness. You’ll notice that active voice often leads naturally to the use of first person (“We collected ...”), which is increasingly common in scientific prose, a trend also endorsed by the AIP (p 14) and other editorial panels. In addition to the use of active and passive voice for clarity and emphasis, scientists sometimes use these stylistic features strategically to highlight or minimize—to make “stylistic arguments.” For example, note how Mallin et al. (1995) use passive voice in their introduction when describing their own research, but active voice when describing the new dinoflagellate they are investigating (Chapter 11, pages 328–330). The effect is to put the new dinoflagellate in the forefront, to call attention to its “active” existence and thus its toxicity, while downplaying the role of the researchers in discovering it.

Chicago Manual of Style, 16th ed., p 5.115

As a matter of style, passive voice (the matter will be given careful consideration) is typically, though not always, inferior to the active voice (we will consider the matter carefully).

American Medical Association Manual of Style

In general, authors should use the active voice, except in instances in which the author is unknown or the interest focuses on what is acted upon.

Here are excerpts of style guides from some noteworthy scientific journals:

Nature

Nature journals like authors to write in the active voice ("we performed the experiment ..." ) as experience has shown that readers find concepts and results to be conveyed more clearly if written directly.

Science

Use active voice when suitable, particularly when necessary for correct syntax (e.g., “To address this possibility, we constructed a lZap library …,” not “To address this possibility, a lZap library was constructed …”).