When it comes to using the active and passive voice in scientific writing, people tend to have extremist tendencies. Some senior researchers will take the phrase “this research was performed” to their graves, and some editors would rather chew glass than allow “it has been hypothesized” to leave their desk unaltered. Militant positions on the active and passive voice often arise because few scientific authors and editors understand why each actually exists in the language and how they can be used as tools for focus and emphasis.
To flow and make sense, a paragraph should focus on one main idea. This often takes the form “A does B” or “B is done by A”. What’s the difference? Why write one over the other? (Aside from reasons like “that’s the way I was trained, dammit” and “that’s the rule and I don’t care what you say”.) Whether “A does B” or “B is done by A” is better depends on whether A or B is your main character.
When we read a sentence, we expect the grammatical subject to be the focus of the story. Our brains understand things in terms of stories and their main characters. So, if you choose who your main character is, and structure your sentences around it, it makes the text feel like you’re telling a focused, coherent story about something. For example, let’s say you’re writing a paper, and an introductory point is that the pancreas produces insulin.
The pancreas produces insulin.
This sentence in the active voice is a fine start for a story about the pancreas. The pancreas is the grammatical subject of the sentence, so we expect the pancreas to be the subject of the paragraph. But, if you’re actually going to talk mainly about insulin and what it does– that is, insulin is your main character– the following version would better help guide the reader in that direction:
Insulin is produced by the pancreas.
With the passive voice, we’ve put insulin as the subject. Now, we expect to hear more about insulin (rather than the pancreas). Who appears first in the sentence changes our expectations about the story we’re going to hear, and what makes academic writing confusing is when these clues don’t match what actually follows. So, whether you should write a sentence in the active or passive voice depends on whether your main character is doing something (ex. X regulates some process, active voice) or is having something done to it (ex. X is regulated by something else, passive voice).
Here’s an excerpt from an abstract that effectively matches the main character and the grammatical subject, using both the active and passive voices when appropriate:
Verbal and mathematical models that consider the costs and benefits of behavioral strategies have been useful in explaining animal behavior and are often used as the basis of evolutionary explanations of human behavior. In most cases, however, these models do not account for the effects that group structure and cultural traditions within a human population have on the costs and benefits of its members’ decisions. Nor do they consider the likelihood that cultural as well as genetic traits will be subject to natural selection. In this paper, we present an agent-based model that incorporates some key aspects of human social structure and life history.
In nearly all of the sentences, “models” is the grammatical subject. It’s the subject both when the models are doing something (active voice, “the models do not account for…”) and when they’re having something done to them (passive voice, “models…are often used…”). Because “models” is the subject, we feel that we’re going to read a story about models. That’s exactly what we get, so the abstract seems clear and focused. (I might now go read this paper, because it sounds interesting.)
Now take a look at this undone version. I’ve changed active to passive, passive to active, and reorganized to create a mismatch between the grammatical subject and the main character (the models):
Animal behavior has often been explained by verbal and mathematical models that consider the costs and benefits of behavioral strategies, and researchers have used these models as an evolutionary basis to explain human behavior. In most cases, however, the effects that group structure and cultural traditions within a human population have on the costs and benefits of its members’ decisions are not accounted for by these models. The likelihood that cultural as well as genetic traits will be subject to natural selection are also not considered. In this paper, we present the incorporation some key aspects of human social structure and life history in an agent-based model.
Exactly the same content is here, but a reader may not even make it to the end of the abstract, because it sounds long-winded and unfocused. There’s nothing wrong with each sentence- but they don’t “gel” together as a story. That’s what strategic sentence structure can do for you!
Patricia Gongal works with researchers to improve the structure, clarity, flow, and style of their scientific writing, and has lots of opinions about science and academia.