Use of personal pronouns in papers (research, etc.)

Back at university, I remember being told to never use personal pronouns in my dissertations. I was never given a reason, but I was told to avoid statements like

The evidence leads me to believe.

or

After researching similar techniques I had settled on ....

I remember spending a lot of time constructing sentences that used "the author" rather than "I" or similar. These are some very bad examples (as I submitted my final dissertation back in 2008).

Since then however, when I've read research papers, scientific articles and dissertations the authors have referred to themselves as "I" or "us" (when collaborated on). This seems to fly in the face of what I was told at university.

Is there a hard-and-fast rule to this, or is it down to personal preference?

Answer

There is a discussion on the perceived advantages and disadvantages of the use of the passive voice in scientific registers at https://cgi.duke.edu/web/sciwriting/index.php?action=passive_voice .

The article begins:

Passive Voice in Scientific Writing

Few topics engender such heated debates as that of active vs. passive
voice. This argument is relevant to writing in general, but I think
it's particularly so to scientific writing. Some writers speak out in
vehement opposition to passive voice, others claim it should be used
liberally. What is one to do?

Everyone will have to make his own decision. I think the most

important thing is that you've thought about it and you make the
decision consciously. At the risk adding to an already saturated
debate...

Use of the passive, without 'by-phrases', is (almost?) essential in 'depersonalised' writing, though it can be difficult on occasion for the writer to avoid pompous or ridiculous-sounding phraseology.