When to Use the Active or Passive Voice in Research Writing
One decision that gives pause to thousands of beginning researchers is whether to use the active or passive voice in their research papers. You may have been taught in school that you should always use the active voice, especially when giving speeches and when writing fiction or persuasive essays, as it emphasizes the subject and makes your sentences leaner and stronger.
While this rule generally applies to research writing, there are some definite differences in application–this accounts for why there are so many sentences in scientific journal articles using the passive voice construction. In fact, applying only one type of voice construction can make a paper awkward to read and difficult to comprehend, and it might even confuse the reader about which parts of the study or a given passage are most important. So when should an author choose the passive voice over the active voice and what is the difference between the two?
Differences Between the Active and the Passive Voice
In general, the active voice emphasizes the agent of the action—that is, the person or object performing the action.
Example: “We arranged the sample groups.”
The subject pronoun “we” leads the sentence, setting off its importance in the action and leading right into the action taken against the object, “the sample groups.” Using this construction doesn’t necessarily imply that “the sample groups” is unimportant, but it does place special emphasis on the agent of the action.
The passive voice, on the other hand, emphasizes the person or object receiving the action.
Example: “Sample groups were arranged (by us/by the researchers).”
In this example, “sample groups” stands out as the most important element in the sentence, and indeed it should since we are able to omit the agent entirely—adding “by us” or “by the researchers” seems redundant as the researchers are necessarily the ones carrying out the operations of a study. Also, note that by eliminating the agent we have also decreased the word count, which makes the passive construction leaner than the active voice in this case.
Since active-voice constructions are usually stronger, clearer, more direct, and often more concise than their passive-voice counterparts, most style guides advise scientific and clinical authors to favor the active voice in their research writing.
However, this is not a command to silence the passive voice entirely. In fact, scientific manuscripts have increasingly favored passive-voice construction in the past couple of decades. Whether the reasons for this are practical or because it is simply more fashionable today to use the passive voice, there are good reasons to include this construction to gain a balanced perspective in your writing.
Sticking with the conventional wisdom that we should use the active voice as often as possible, when exactly should we opt for the passive? Here are three circumstances in which using the passive voice can be a good decision.
1) When the agent of the action is unimportant, unknown, or obvious to readers
Choose the passive voice when the agent of the action is unknown or unimportant to the action being discussed, or when it is quite clear who is performing the action. In some cases, you may identify the agent using a “by” clause, but it is often unnecessary to add this information.
Examples of active and passive voice:
“Over 20,000 patients are diagnosed with diabetes each year (by doctors) in the United States.”
“Encyclopedias have been written (by scribes and scholars) throughout history.”
“Carcharodon carcharias has been studied (by scientists) more extensively than almost any other species of shark.”
In the first example, naming the agent of diagnosis is redundant, as doctors are almost universally the ones who diagnose diseases. In the second example, the author assumes the reader will not be interested in the authors (this decision of course depends on the focus of the study) or perhaps the authors are unknown; the agent may be added in case this information is known and is somewhat important to the statement. In the third example, the agent is fairly obvious, as scientists are the ones tasked with studying species of animals.
2) When the object or action itself is more important than the agent performing the action
In research writing, the study is clearly of greater importance than the researcher undertaking the study (unless that researcher happens to be someone as renowned as Stephen Hawking), and thus the passive voice is more often employed. This object/action focus can commonly be seen in the Methods section, in which an author writes about what he or she did (or rather, “what was done”), mostly using the passive voice since the topics here are generally the research methods, materials, and procedures.
Examples of active and passive voice:
“Frozen embryos were stored in a cryogenic tank for two weeks.”
“The extract from sample A was added to sample B to create a mixture.”
“The results were assessed using a Chi-square statistic.”
The sentences might be written in the active voice like so:
“We stored the embryos in a cryogenic tank for two weeks.”
“We added the extract from sample A to sample B to create a mixture.”
“Our team assessed the results using a Chi-square statistic.”
What would be the net benefit of using the active voice here? In none of these examples would the active voice improve the sentences by shortening them or by clarifying the focus of the action. The length of each active sentence is the same as its passive voice counterpart, and the sentences in the active voice actually redirect the focus to the agent—“we” or “our team”—which does not seem to be the most important element in any of these examples. The active-voice constructions are admittedly a bit stronger and livelier, but they seem more fitting for a short story or anecdote than for an explanation of actions carried out in the course of a scientific study.
Another benefit of using the passive voice in the Methods section (in addition to some other parts of the research paper) is that it varies the structure and cadence of your sentences while maintaining an emphasis on the actual work. One can see how a paper becomes more readable when there isn’t constant emphasis on only one part of a sentence.
In the Methods and other sections of the manuscript, use the passive voice to redirect focus to the work being done—the object of the action or the action itself. When editing a manuscript, note this distinction in voice usage between the Methods section and other sections, as it is a common one in research writing.
3) When the recipient of the action is the topic of your sentence
It is sometimes necessary to use the passive voice to place the most important information at the beginning. By placing an item at the beginning of a sentence, you are putting it in the “topic position” (or “subject position”), indicating that it is the central element of your sentence.
Similarly, by placing a word at the very end of your sentence, you put it in the “stress position,” which is often used for words or phrases that modify or qualify the primary focus of your sentence. You can place words in these positions using passive or active constructions.
Examples of active and passive voice:
Active voice: “Scientists once classified slime molds as fungi, but they no longer classify them as part of that particular kingdom.”
Passive voice: “Slime molds were once classified as fungi but are no longer considered to be part of that particular kingdom.”
In the first example, “scientists” occupies the topic position, and “part of that particular kingdom” is in the stress position. What might this ordering indicate to the reader? First, it shows that “scientists” is perhaps the main focus (or at least an important element) of this information. Second, by putting “part of that particular kingdom” at the end of the sentence, the author seems to be telling the reader that this qualifying information is also essential to understanding this information.
How might this information be interpreted differently in passive-voice construction? The main difference here is that “slime molds” are placed in the topic position, indicating that they are the primary focus of this information.
Privileging One Element Over Another in a Sentence
Which voice you use and how you order your sentence elements can make a big difference in establishing the importance of one element over another, especially when both of these are important to your study and neither involve the researcher.
In the following examples, there are at least two elements that the study focuses on. Reordering these by changing the voice makes the importance of these positions quite clear.
Examples of active and passive voice:
Active voice: “These amoeba coalesce into a multicellular, slug-like coordinated creature that grows into a fruiting body.”
Passive voice: “This multicellular, slug-like coordinated creature, which eventually grows a fruiting body, is created by coalescing amoeba.”
In both of these sentences, the “amoeba” and the “multicellular, slug-like coordinated creature” are central; they seem to be essentially two parts of one process. This process is demonstrated through the active construction, which explains the life-cycle chronologically and therefore places emphasis on both elements (both agents) equally: “amoeba” and “fruiting body” (in the topic and stress position respectively) are at the beginning and end of this sentence and the particular part of the life cycle, with the information in the middle representing the transition between the two.
However, in the passive-voice construction, the “multicellular, slug-like coordinated creature” is in the topic position, the “amoeba” in the stress position, and the “fruiting body” in the middle is described (using a relative clause) as an outgrowth of this “creature.” This ordering completely shifts the focus of the sentence to the multicellular creature itself, with the other elements acting as supporting information. But because “amoeba” is still included in the sentence and is in the stress position, the author clearly wants to show its importance.
Combining the Active and Passive Constructions in a Sequence of Sentences
Whether introducing the purpose of your study in the Introduction section or suggesting further applications or studies in the Discussion and Conclusion, you should try to combine conciseness and clarity of intention to create a logically cohesive structure. This can be done by combining passive and active constructions.
One way to achieve this is to create a structure that “connects backwards”—the final sentence in your paragraph or short sequence of sentences explains the purpose of the first sentence. Let’s see how this might work in action in the Introduction section.
Example of three cohesive sentences (active—passive—passive):
[Excerpt from “A Possible Correction of the Face Inversion Effect: A Methodological Commentary” (Rakover, Sam and Cahlon, Baruch)]
“The present commentary concerns the face/object (UI) effect. This effect can be explained by appeal to either innate or learning factors. However, this effect can also be influenced by another factor, the ‘baseline-level,’ which is the focus of the present commentary.”
These three lines occur in sequence within the paper’s Introduction section. The first sentence clearly and directly explains the problem of the study (“the face/object (UI) effect”) using the active voice, setting the reader up for a further explanation to follow.
The second sentence, written in the passive voice, explores some potential directions from which this problem can be approached.
And the third sentence unites the two ideas, or “synthesizes” them, using a passive-voice construction. This third sentence has a parallel structure to the second and unites the problem and the proposed explanations using the word “influence” as a unifying action.
By focusing on the topic (“the effect”), the author can create a cohesive structure that uses sentences in both the active and passive voice. Such a passage flows naturally and is more comprehensible and enjoyable for the reader than separated sentences using the same voice construction.
Active and Passive Voice Guidelines
There are several good reasons to vary your sentences between active and passive voice:
- To place emphasis on the most important element of the sentence
- To cut down on word count (sometimes using active, sometimes using passive)
- To make your paper easier for the reader by creating variations in cadence and syntax
As a rule of thumb, choose the active voice whenever possible.
Choose the passive voice when there is good reason to do so. Consider passive voice when:
- The agent is unknown, unimportant, or obvious to the reader
- The agent is less important than the action of the sentence
- The agent is less important than the topic of the sentence
- One topic (among several) has greater importance
- Springer.com. “Stress Position” https://www.springer.com/gp/authors-editors/authorandreviewertutorials/writinginenglish/stress-position/10252690
- Gopen GD, Swan JA. The science of scientific writing. Am Scientist. 1990;78:550-558.
- Rakover, S., & CAHLON, B. (2014). A Possible Correction of the Face Inversion Effect: A Methodological Commentary. The American Journal of Psychology, 127(3), 303-311. doi:10.5406/amerjpsyc.127.3.0303 Website: https://www.jstor.org/stable/10.5406/amerjpsyc.127.3.0303?seq=1#page_scan_tab_contents
- Wordvice Blog: “Which Tenses to Use in Your Research Paper.” https://blog.wordvice.com/video-which-verb-tenses-should-i-use-in-a-research-paper/
- Wordvice Blog: “How to Choose the Best Title for Your Manuscript.” https://blog.wordvice.com/best-title-for-journal-manuscript/
- Wordvice YouTube Channel: “How to Create a Title for Your Research Paper.”
- Wordvice Blog: “Choosing the Best Keywords for Your Paper.” https://blog.wordvice.com/choosing-research-paper-keywords/
- Wordvice YouTube Channel: “Parts of a Research Paper.” https://www.youtube.com/watch?v=aO6ipI-d2fw
- ScienceDocs Inc. Blog: “5 Common Mistakes to Avoid When Writing a Discussion.” https://www.sciencedocs.com/writing-a-research-paper-discussion/