Many people are confused by whether they are using the active or passive voice when writing, and in which scenario each is preferred. Thankfully, there is a simple way of identifying the two styles; the key to understanding the difference between them is to spot the subject and the object in each sentence, and then selectively order the way you introduce them.
In an active sentence, the subject is the focus of the sentence (the element that is doing the action), whereas the object is the element that is receiving the action. In contrast, in a passive sentence, the element targeted by the action is promoted to the subject position and becomes the focus of the sentence. This can sound confusing, but a good way to learn this concept is to realize that a passive sentence will result in the subject effectively doing nothing, because whatever is happening is being done to it.
Many people confuse ‘voice’ with ‘tense’ and it is important that you learn they are two very different things; both active and passive voice sentences can be written in any tense (present, past, future etc.).
1A: Consider the following active voice sentence:
Phil weighed the mice on weighing scales every week.
‘Phil’ is the subject here, because ‘Phil’ is the person doing the action (weighing) reported in this sentence, whereas the mice are the objects, because they are receiving the action (being weighed). It cannot be a passive sentence because the subject is doing something to the object (weighing it).
1P: Now, consider the passive voice version of the previous sentence:
The mice were weighed by Phil on weighing scales every week.
The mice have become the subject here because they have been promoted to the focus of the sentence. This cannot possibly be an active sentence because the subject is effectively doing nothing, whereas in the active version (1A). the subject actually did something (the weighing).
2A: Consider the following active voice sentence:
More than 50,000 students applied to <snap style="color:blue">Oxford University last year.
‘More than 50,000 students’ is the sentence subject here, because these students are the focus of the sentence (and doing the applying), whereas ‘Oxford University’ is the object because it is receiving the action (the applications). It cannot be a passive sentence because the subjects are doing something (applying) to the object.
2P: Now, consider the passive voice version of the previous sentence:
Oxford University was applied to by more than 50,000 students last year.
‘Oxford University’ is the subject of the sentence here, but you know the sentence must be passive because the subject is effectively doing nothing; the ‘more than 50,000 students’ are the ones doing the action (applying).
Note: Another trick that can often highlight sentences written in the passive voice is to look for the verb ‘to be’. For example: “The exam was administered by the teacher,” and “The matches were played by the teams” are both passive voice sentences, whereas “The teacher administered the exam,” and “The teams played the matches” are the active versions.
However, there are pitfalls to this, which is why it is better to learn this concept as set out initially. For example: “Professor Canuck wants to be recognized as the leading researcher in his field,” is an active sentence but still includes ‘to be’. It is active because the subject is performing the action (the wanting) on the object.
Why does this matter?
In the examples listed above, the passive versions are not especially long-winded, yet if you re-examine them you will notice that they feature more words than their respective active versions. This is of great relevance to you as a science writer because it is very important that you always try to communicate things as concisely as possible. When you start to write more complex sentences, the difference in word count can be large when you compare the active and passive versions, and this is important in a setting in which waffly, vague statements are always your enemy.
Along with a lack of conciseness, ambiguity (being vague) is the other unwanted attribute that comes with the use of passive voice sentences. For example, consider the following active and passive versions of a sentence that might appear in the Methods section of your lab report:
3A: Professor Roberts kept the mice in their cages for three weeks. He then released them into the wild and recaptured them three weeks later.
3P: The mice used in this experiment were kept in their cages for three weeks before they were released and then recaptured after they had spent three weeks in the wild.
Note firstly that the active version features 24 words in comparison to the 30 in the passive one, yet, importantly, the active version explains exactly what happened and who did what, whereas the passive one leaves these specific details out.
Questions 1, 2, 3, 4 and 5 (1 mark each, 5 marks total)
For questions 1, 2, 3, 4 and 5 you should read each sentence and decide whether it is written in the active voice (or not).
Question 1 (1 mark)
The scientists were embarrassed by a mistake that appeared in their journal article.
Question 2 (1 mark)
The scientists realized that they needed to state their argument more clearly when they saw it in the journal.
Question 3 (1 mark)
According to one reviewer, an ethics protocol had also been violated by them.
Question 4 (1 mark)
On a more positive note, the researchers improved their writing skills considerably when they first prepared the article.
Question 5 (1 mark)
It had been thought by some of them that science was just about working in a laboratory until time was spent watching monkeys in the jungle.
Questions 6, 7, 8 (1 mark each, 3 marks total), 9 and 10 (2 marks each, 4 marks total)
For questions 6, 7, 8, 9 and 10, you need to read the passive voice versions of different sentences and then re-write them in the active voice. Questions worth two marks require two changes (from passive to active).
Question 6 (1 mark)
Passive Version: Very little is known by us about the eating habits of the snow leopard.
Question 7 (1 mark)
Passive Version: Over the last 20 years, there has been an enhanced effort made by conservationists to educate the public about the importance of preserving leopard habitat.
Question 8 (1 mark)
Passive Version: But have we been persuaded by researchers that habitat loss is to blame for snow leopards becoming rarer?
Question 9 (2 marks)
Passive Version: The exam booklets were carefully collected by the teaching assistants, before they were ordered alphabetically by a sorting machine.
Question 10 (2 marks)
Passive Version:Many of my classmates found the exam too difficult to complete, but it was still considered by them to be a fair one. I found it quite easy overall, but some questions had obviously been designed to be very difficult by the instructors.
Question 11 (8 marks)
Are the following sentences written in the active or passive voice? Copy and paste the whole set of eight sentences and then answer either 'active' or 'passive' for each one.
- Sentence 1: Students often find it difficult to differentiate between the active and passive voices.
- Sentence 2: Writers and presenters know how important it is to learn these differences, however.
- Sentence 3: In most cases, the active voice is preferred by communicators.
- Sentence 4: People generally express their thoughts more concisely when they use the active voice.
- Sentence 5: For this reason, it is believed by us (as instructors) that long-winded, passive sentences are harder to follow.
- Sentence 6: Yet there are times when you should preferentially use the passive voice.
- Sentence 7: Some of these examples will be highlighted by instructors (and in these guides) over the course of your studies.
- Sentence 8: But when you are in doubt, we encourage you to use the active voice.
Verbs and the active and passive voice
By now you should feel more comfortable changing the style of a sentence from active to passive, and vice versa. As a quick recap, recall that you use the active voice when the subject performs the action on the object. For example, you might write: “Professional footballers will kick footballs harder than amateurs.” Now recall that to make the above sentence passive you would ensure that the subject has the action performed on it (so that it is effectively doing nothing). For example, you would write: “Footballs will be kicked harder by professional footballers than amateurs.”
Look closely at the two sentences and see that the verb (the action/doing word) changes form between the active and passive voice. In the above example, the verb - ‘to kick’ – changes from ‘kick’ in the active voice to ‘kicked’ in the passive voice.
Depending on the verb, and the structure of the sentence, it might not always be different. However, it is very important that you learn to use the correct form of a verb when using one style of voice, and particularly if you write sentences that switch simultaneously between the two.
Question 12 (10 marks)
Fill in the blanks in the following sentences with the correct form of the verb attached to each topic:
A: Topic = evolution, verb = to specialize
- Active: Over time, different bird species will [?????] in eating one type of seed.
- Passive: Different bird species may be [?????] in eating one type of seed.
B: Topic = competition, verb = to eat
- Active: In our study, we noticed that stronger individuals [?????] the best food because they out-competed the weaker ones.
- Passive: Weaker individuals may have been forced to [?????] poorer quality food than stronger ones because they were out-competed.
C: Topic = designing an experiment, verb = to begin
- Active: The researcher [?????] reading literature a long time ago to get ideas about what sort of experiment to design.
- Passive: The process of designing an experiment was [?????] by the researcher reading literature to get ideas about the general topic.
D: Topic = global warming, verb = to prevent
- Active: Many climatologists believe it is now impossible to [?????] global warming.
- Passive: [?????] global warming is now believed to be impossible by many climatologists.
E: Topic = laboratory experiments, verb = to replicate
- Active: My professor thinks that [?????] the experiment will improve the strength of the conclusions.
- Passive: I was asked to [?????] the experiment by my professor as it is thought that this will improve the strength of the conclusions.