I studied literature twentyfive years ago and now study psychology. When I dealt with literary theory and analysis a quarter of a century ago, I learned to avoid any direct reference to myself by using convoluted sentence structure and passive voice. If I could not avoid that reverence or needed to use it, I would use a pluralis majestatis to inluce both the author(s) and the readers. This worked, because usually what was described in those texts was in fact actively done by both authors and readers: "Looking at the plot, we can see that ..." – and of course the readers can see what the author sees as well. Otherwise it would not be objective and therefore not scholarship. So that plural is fitting.
In psychology (and other natural sciences), articles usually describe an experiment and its results. The experiment is not conducted by the readers, but by the author(s) of the article. So the rule is to refer to the author(s). If it is one author, this person refers to him- or herself as "I". If it is a team, they write of themselves as "we". Simple and straightforward.
If the authors believe something, they write "We believe" and argue why they do so. (In the natural sciences, belief is not worth much, you want proof. So you won't find a sentence like that very often.)
If the study found something, you write: "There is a significant correlation between ...". No need to write about the study at all. Just stick closely to the facts. The only time you refer to the study is when you describe its place in the research history: you undertake that study, because you want to find out if ... After that you describe what you do, what comes out, and how that relates to other studies.
The study does not show anything! In science there can always only be proof against something: Hypothesis: All swans are white. Observation: Black swan. Result: Hypothesis disproved. You can never prove anything!!! Because you cannot observe everything everywhere always. Even if in fact all swans are either white or black, you can never be sure, because maybe there was one brown mutation a hundred years ago (or will be a hundred years in the future). So studies do not show anything, you can only disprove a hypothesis. And that you can write like that. No need to refer to the study at all.
The best practice is always to pick a selecton of professional publications in your field and do like they do.