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Using the passive or active voice

Should I use the passive or active voice in my academic text?

The choice of the active or passive voice is one of the most controversial issues in academic writing. Common advice is that the active voice is preferred, on the grounds that it makes a sentence shorter and clearer. Compare these two sentences:

  • Active voice: Smith et al (2015) performed a mixed-effects modeling analysis.
  • Passive voice: A mixed-effects modeling analysis was performed by Smith et al (2015).

However, the active voice may not always be the best choice. Academic writing is by definition formal and impersonal, and the passive voice helps convey that tone. It is particularly suitable when what is being performed is more important than the subject performing the action. This is often the case in research papers (as opposed to a Master’s dissertation or PhD thesis), and in STEM disciplines especially. See how the passive voice in the sentence below reads as more impersonal:

  • Active voice: In the second experiment, we heated the air from 500 to 1000K.
  • Passive voice: In the second experiment, the air was heated from 500 to over 1000K.

Sometimes the subject of a sentence can be unknown, or even nonexistent. With the below sentence, for instance, an active voice equivalent would be difficult to write.

  • Passive voice: More research is required to understand this phenomenon.
  • Active voice: … ?

If you are still unsure whether you should use the active or passive voice in your academic text, ask yourself the following questions:

  • Am I writing a Master’s dissertation/PhD thesis, or a research paper for a journal?
  • What do I want to focus on: the element affected by the action/the action, or on the subject doing the action?
  • Is the subject performing the action obvious and important?
  • Would my sentence be shorter and more straightforward in the active voice?