Active & Passive Voice: Use Word Order to Reflect Context

Now that we have an idea of how to construct sentences, we can begin by deciding what is important (to be stressed), less important (to be subordinated), and not important (to be omitted). Next, take the reader’s expectations into account, by considering the position of each word. The following table describes the most important positions in a sentence in line with reader expectations.

Topic Position Stress Position
Start End
Old information New information
Familiar Complex
Short Long

The following sentences contain the same facts, but differ in focus. Due to this, they have to be written in either an active or a passive voice. Here, the choice, i.e. the word order, is determined by context, not by convention to use only one voice and not the other.

In the active voice, the subject performs the action. The subject is sand flies, the verb is carry, and the object is Leishmania parasites. Our attention is on sand flies. The sentence emphasises that they carry Leishmania parasites (as distinct from carrying e.g. microsporidia). We would use this sentence if the previous discussion was about sand flies.

Active voice

👍 Sand flies carry Leishmania parasites.

In the passive voice, the subject receives the action. The subject is Leishmania parasites, the verb phrase is are carried by, and the object is sand flies. Our attention is on the Leishmania parasites. The sentence emphasises that they are carried by sand flies (as distinct from being carried by e.g. fleas). We would use this sentence if the previous discussion was about Leishmania parasites.

Passive voice

👍 Leishmania parasites are carried by sand flies.

Use the Active and Passive Voices Appropriately

Aside from allowing word order to dictate active versus passive voice, there are specific cases when we want to use one versus the other.

Use the active voice to claim ownership

Remember, in an active voice sentence, the subject performs the action. The active voice states who or what performed an action. In a passive voice sentence, the subject receives the action.

👎 Considering the robust enrichment for metabolic kinases, a substantial reprogramming of metabolism upon macrophage activation was hypothesized.

👍 Considering the robust enrichment for metabolic kinases we hypothesized a substantial reprogramming of metabolism upon macrophage activation.

👎 It was hypothesized that the changes in profiles of fatty acids may serve as a mechanism for improved cognition.

👍 We hypothesized that the changes in profiles of fatty acids may serve as a mechanism for improved cognition.

Some advantages of the active voice, which is gaining in popularity in scientific literature:

Don’t be afraid to state the agent of an action even if it is I or we when appropriate. However, when using the active voice, the agent is not always human, as shown in the following examples.

The Active and Passive Voices

In an active voice sentence, the subject performs the action. In a passive voice sentence, the subject receives the action.

👍 Macrophages generate nitric oxide metabolites during the immune response. Active voice

👍 Nitric oxide metabolites are generated by macrophages during the immune response. Passive voice

In the Results section, first person pronouns (I and we) can be used with verbs in the active voice to take ownership of a result.

Use Active Voice when Reporting Results

In these sentences from a Results section, the active voice is more effective.

👎 Isolated mitochondria were assayed for nitric oxide synthase activity. Passive voice

👍 We assayed isolated mitochondria for nitric oxide synthase activity. Active voice

We already saw that the choice of word location and placement in a paper can determine the choice of active or passive voice. Another consideration is style, changing the voice of a sentence can make it more concise and readable.

Active Versus Passive Voice Determined by Style

This sentence comes from a Results section, in which the active voice is often preferable. The passive form is not only longer, but also contains a buried verb. Can you find it?

👎 The action potential of ventricular myocardial fibres was determined by direct measurement.Passive voice

👍 We directly measured the action potential of ventricular myocardial fibres. Active voice

The passive voice allows the author to distance himself from his own work, thus facilitating an unbiased viewpoint. However, excessive use of the passive voice leads to dull and dense writing. It can be used effectively in certain situations as shown in the margin note.

Some advantages of the passive voice include:

Note that the passive voice is appropriate in the Materials & Methods section. This is useful if the work described was performed by technicians or third party service providers who are not authors. Moreover, using the passive voice in the Materials & Methods section focuses the action on the topic of interest.

Use Passive Voice when Reporting Materials & Methods

In this sentence from a Materials & Methods section, the topic is cells. Using the passive voice emphasises the specific topic.

👎 We incubated the cells at room temperature for two days.Active voice

👍 The cells were incubated at room temperature for two days. Passive voice

Passive versus Active Voice

Complete the following three tasks for each of the sentences below:

  • Identify if it is written in the active or passive voice

  • Consider if this sentence should be re-written in the other voice. Why or why not?

  • Think about where this sentence would appear in a research article. What purpose does it serve?

  • If you think it should be re-written, do so in the space provided.

  • Betaine was administered to rats orally through a syringe fitted with a ball-type feeding needle in a volume of 0.2 ml per rat per feeding.

  • When lithium was administered to rats prior to sacrifice, renal GSH level, but not hepatic GSH level, was increased significantly.