My high school science teachers always preached the use of the passive voice in scientific writing, especially in the methods section, like so:

“The samples were removed from storage and immediately freeze-dried at -80°C for 18 hours”

I can understand why. Passive voice is a quick and dirty way to make your writing sound sciencey. It’s dry and formal, and sounds like something you would read in a government report. It’s perfect for convincing your teacher or your peers that you are a very knowledgeable student or scientist; if they’re just as knowledgeable as you it should be easy to understand. So why is active voice so much better?

Active voice attributes agency

Scientific experiments don’t spontaneously occur as a part of the normal actions of the universe. Even if your experiment does, at some point you’ve played an active part in measuring or gathering data (perhaps with the exception of highly theoretical work). When you write in active voice, you are forced to think on and be honest about your part in your experiment. The choices you made in experimental manipulations, processing samples and statistical analyses all have some effect on what you discover. Writing your methods using an active voice acknowledges to your readers the part you play in your experiment and might help you conceptualise your role and effects better.

Active voice usually sounds nicer

Active voice tends to lead to less cumbersome sentence structures. Taking our previous example:

“The samples were removed from storage and immediately freeze-dried at -80°C for 18 hours”

…becomes…

“We removed the samples from storage and immediately freeze-dried at -80°C for 18 hours”

Way easier on the mental palate, don’t you think? Active voice makes your writing more accessible and entertaining (if that’s even really possible for the methods section in science). Of course, accessibility is antithetical to some fields that I am aware of, where heavy jargon and convoluted grammar are employed to keep lay people out of consumption and contribution – I’m looking at you lawyers.

Dealing with excessive active voice

Too much active voice can sound clunky if you aren’t careful. I work in metabolomics, where we use analytical machines with quite a large number of settings to tweak. These can lead to incredibly repetitive parts of the methods section:

“We used a C18 column …
“We applied a collision energy of …”
“We used solvent A, acetonitrile with an additive …”

We, we, we! Using “we” all the time like this starts to sound silly. I get creative with my active voice to help keep my readers from fatiguing or laughing out loud. One of the easiest ways is to use adverbials, like so:

“Prior to processing, we removed samples from storage …”
“Using a freeze dryer, we extracted excess water from the samples”

Discourse markers are equally helpful:

“Firstly, we removed the samples from storage.”
“Then, we proceeded to freeze dry the samples at -80°C.”
“Finally, we measured the dry weight of each sample.”

In the depths of the methods section, where I’m listing pieces of analytical equipment and their settings, I’ll often switch to “our” instead of “we”:

“We used a reverse phase C18 HPLC column”

…becomes…

“Our HPLC column was a reverse phase C18 column”

This phrasing isn’t better per se, but after a long paragraph of sentences that start with “We used”, “Our” is quite refreshing

The case for passive voice

Don’t throw passive voice out with the bathwater just yet. It still has a place in scientific writing, but just not as a default. Passive voice’s superpower is to bring the object to the beginning of a sentence and removing the subject entirely:

Active: “We removed the samples from storage …”

Passive: “The samples were removed from storage …”

As I discussed earlier, this removes the attribution of agency of the scientist and make it sound like the process just happened. For this reason I almost always use active voice in my scientific writing, but I occasionally use passive voice when a sentence sounds particularly clumsy using active voice, and it is already clear that “we” performed the action from the context of the previous text.

References

I have adopted this style of writing because of the work of Steven Pinker and Rupert Sheldrake.