Human orthopedic introductions were more direct and concise than veterinary orthopedic introductions. Veterinary abstracts and discussions combined were on average 563 words longer, that is, over a page longer than human orthopedic introductions and conclusions combined.
We informally assessed causes for the difference in word count. It appeared that the veterinary articles provided more background and ancillary information than provided in human articles. Both introductions and discussions had elements similar to review papers, rather than focused explanations of the gaps in literature and a narrow discussion of the results.
Veterinary articles sometimes have more redundancies. For example, the human introductions stated aims, but veterinary articles often stated both aims and hypotheses. From the point of view of the reader, providing general hypotheses after stating aims can be redundant.
The veterinary introductions had 22.6% fewer active voice sentences than the human introductions, and most veterinary introductions had fewer active sentences than most human articles. For perspective, one human article introduction in this study had 100% active sentences.
However, sometimes authors prefer the passive voice to emphasize the object of a sentence rather than the subject. For example, the passive sentence, “The force plate was walked over by the dogs,” emphasizes the force plate.
Still, authors could emphasize the force plate actively with, “The force plate was used to assess ground reaction forces. Dogs walked over it five times.”
Sometimes writing in the active voice also requires the first-person voice, “I” or “we,” because the scientist performed the action: “We walked the dogs over the force plate.” In the past, scientific writing experts discouraged the first person because it placed emphasis on the authors. But does that matter? Consider the clarity of the first sentence of Watson and Crick (1953), “We wish to suggest a structure for the salt of deoxyribose nucleic acid (D.N.A.). (11) That first-person, active voice sentence is clear compared to the passive alternative, “A structure for the salt of deoxyribose nucleic acid (D.N.A.) is suggested in this paper.”
Contemporary readers prefer the first person because it is easier to read. Important scientific journals, such as Nature, and the British Medical Journal prefer using “I” and “we” to awkward, passive wording that reduces clarity. (3, 4, 12) An active voice is easier to understand for readers whose first language is not English. (12)
We acknowledge that the active voice is only one aspect of clarity. There are subjective attributes, such as noun clustering, organization, and repetition, but they can be hard to assess and quantify. (5)
This study focused on the introduction and discussion sections because they offer more opportunity for direct and concise writing than materials and methods sections, and results sections. Informally, the materials and methods sections and results sections of the human and veterinary articles appeared to have the same structures and terse reporting style. In other words, the human articles did not shorten their introductions by leaking introduction information into the materials and methods sections.
Different study designs and research topics might by necessity have considerably different introduction and discussion lengths. For example, medical articles involving public policy can have very long discussion sections. That is why we focused on a specific kind of study, orthopedic randomized clinical trials, to control variation.
The community of veterinary orthopedic clinical trial authors is relatively small compared to human authors. Some veterinary authors co-authored more than one veterinary article. There is no way to assess the correlated-author effect on outcomes without designing a study to do so. No author appeared as lead author more than once.