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Clear Science Writing: Active Voice or Passive Voice?


What Is Active Voice?

An author may write a sentence in one of two "voices"—active or passive.

The active voice emphasizes the performer (or agent) of the action:

Wind disperses plant seeds.

Smith et al. investigated the relationship.

We have analyzed the results.

The active voice is direct (performer–verb–receiver), vigorous, clear, and concise. The reader knows who is responsible for the action.


What Is Passive Voice?

The passive voice, in contrast, emphasizes the receiver (or product) of the action:

Plant seeds are dispersed [by wind].

The relationship was investigated [by Smith et al].

The results have been analyzed [by us].

The passive voice is indirect (receiver–verb–performer) and can be weak, awkward, and wordy. Passive voice uses a form of the verb to be followed by a past participle (e.g., dispersed, investigated) and a by phrase. If the by phrase is omitted (the truncated passive), the reader will not directly know who or what performed the action.

A particularly awkward and ambiguous form of the passive voice occurs when an author uses it as the receiver rather than the first-person pronouns I or we:

It is concluded that the treatment is effective.

These types of passive-voice sentences are a form of hedging.


In addition to being awkward, sentences written in the passive voice, if not constructed carefully, may contain grammatical errors such as dangling modifiers.

Changing from passive to active voice corrects the error and strengthens the sentence:

Dangling: To investigate the source of nutrients, eggshell membranes were compared. (incorrect passive)

Correction: To investigate the source of nutrients, we compared eggshell membranes. (active)

Dangling: After analyzing the samples, the plants were measured daily. (incorrect passive)

Correction: After analyzing the samples, we measured the plants daily. (active)

Despite these disadvantages, the passive voice has a legitimate place in writing. In addition to allowing an author to vary the sentence structure, the passive voice has other important functions. To learn more, see "The Value of the Passive Voice."


Tradition and the Passive Voice

More than a century ago, scientists typically wrote in an active style that included the first-person pronouns I and we. Beginning in about the 1920s, however, these pronouns became less common as scientists adopted a passive writing style.

Considered to be objective, impersonal, and well suited to science writing, the passive voice became the standard style for medical and scientific journal publications for decades.

There were exceptions, however. For instance, in 1953, one elegantly written paper began:

We wish to suggest a structure for the salt of deoxyribose nucleic acid (D.N.A.).1

The opening sentence of Watson and Crick's classic article is simple, direct, and clear. But suppose the authors had taken the passive point of view:

In this paper, a structure is suggested for the salt of deoxyribose nucleic acid (D.N.A.).

The emphasis is now on the receiver of the action (the structure), but at a price—the sentence has lost its clarity (who suggested?), energy (passive verb), and overall impact.


Emphasize the Active Voice

Nowadays, most medical and scientific style manuals support the active over the passive voice.

For example, the American Medical Association's AMA Manual of Style recommends that "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."2

The Publication Manual of the American Psychological Association (APA) has similar advice: "Prefer the active voice....The passive voice is acceptable in expository writing and when you want to focus on the object or recipient of the action rather than on the actor."3

These manuals and other books on science writing recommend using the active voice as much as possible. An author may decide to focus on the receiver—and thus use the passive voice—when the performer is unknown or of less importance. For many authors, this occurs most often in the Methods section.

Do scientific and medical journals, in their instructions for authors, advise them to write in the active voice?

Many journals indirectly do so by referring authors to a style manual that supports the active voice, or by publishing articles in which active-voice sentences are common and acceptable.

Although some journals ask authors to limit first-person pronouns or restrict them to certain sections, others not only encourage authors to write in an active style, but prefer them to use first-person pronouns over passive voice. Here is a small sampling:

Behavioral Ecology: "The first-person active voice is preferable to the impersonal passive voice."4

British Medical Journal: "Please write in a clear, direct, and active style....Write in the active [voice] and use the first person where necessary."5

The Journal of Neuroscience: "Overuse of the passive voice is a common problem in writing. Although the passive has its place—for example, in the Methods section—in many instances it makes the manuscript dull by failing to identify the author's role in the research....Use direct, active-voice sentences."6

The Journal of Trauma and Dissociation: "Use the active voice whenever possible: We will ask authors that rely heavily on use of the passive voice to re-write manuscripts in the active voice."7

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."8

Ophthalmology: "Active voice is much preferred to passive voice, which should be used sparingly....Passive voice...does not relieve the author of direct responsibility for observations, opinions, or conclusions (e.g., 'The problem of blood flow was investigated...' vs. 'We investigated the problem of blood flow...')."9

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...')."10


Summary

For vigorous, clear writing, opt for the active voice unless you have good reasons for choosing the passive voice.

Choose the passive voice when the performer is unknown or when you want to focus on the action or the recipient of the action.

Writing from the first-person point of view (I, we), when necessary and natural, is accepted and encouraged by many journals. If you are not sure about a specific journal, however, study its guidelines and recent issues to get a feel for the journal's perspective on the passive voice and first-person pronouns.

When is a good time to use the passive voice in scientific writing? Read the article "The Value of the Passive Voice" to learn more.


Sources



  1. Watson JD, Crick FHC. Molecular structure of nucleic acids. Nature. 1953;171:737-738.


  2. Iverson C, Christiansen S, Flanagin A, et al. AMA Manual of Style: A Guide for Authors and Editors. 10th ed. New York, NY: Oxford University Press; 2007.


  3. American Psychological Association. (2009). Publication Manual of the American Psychological Association (6th ed.). Washington, DC: Author.


  4. Instructions to authors. Oxford Journals Web site: Behavioral Ecology. http://www.oxfordjournals.org/our_journals/beheco/for_authors/general.html. Accessed March 5, 2009.


  5. The essentials of BMJ style. BMJ Publishing Group Web site: British Medical Journal. http://resources.bmj.com/bmj/authors/bmj-house-style. Accessed March 5, 2009.


  6. Westbrook G, Cooper L. Writing tips: Techniques for clear scientific writing and editing. The Society for Neuroscience Web site:The Journal of Neuroscience. http://www.jneurosci.org. Accessed March 5, 2009.


  7. Guidelines for authors. International Society for the Study of Trauma Web site: The Journal of Trauma & Dissociation. http://www.isst-d.org/jtd/journal-trauma-dissociation-info-for-authors.htm. Accessed March 5, 2009.


  8. How to write a paper: writing for a Nature journal. Nature Publishing Group Web site: Nature. http://www.nature.com/authors/author_services/how_write.html. Accessed March 4, 2009.


  9. Guide for authors. Elsevier Web site: Ophthalmology: Journal of the American Academy of Ophthalmology. http://www.elsevier.com/wps/find/journaldescription.cws_home/620418/authorinstructions. Accessed March 5, 2009.


  10. Some notes on Science style. American Association for the Advancement of Science Web site: Science. http://www.sciencemag.org/about/authors/prep/res/style.dtl. Accessed March 4, 2009.


Do you have a question on this writing tip? Simply contact me online and I'll be happy to help.

For information on scientific and medical editing, please visit Science Editing Services.







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