Do we cite authors or papers when using author/year citations?

Question

Numbered citations

In my field, we usually use only numbered citations, e.g.

As shown in [1], the sky is blue.

This means that we obviously refer to a certain the paper (which can be found under [1] in the reference list). Saying something like

As shown by [1], the sky is blue.

doesn't make too much sense, whereas

As shown by Tyndall [1], the sky is blue.

works.

Author / year citations

Do we again cite papers when using author / year citations? Is "Tyndall, 1869" our name for a certain paper? Or are we refering to the authors?

In particular, which of this is correct:

1. As shown in Tyndall (1869), the sky is blue.

2. As shown by Tyndall (1869), the sky is blue.

3. As shown by Tyndall (Tyndall, 1869), the sky is blue.

4. As shown in (Tyndall, 1869), the sky is blue.

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Sorry if this is a duplicate. This question and the answers don't really help.

Answer 1

In general, the final arbiter of this is the style guide the editor is using for the book, journal or collection. If you have no external editor or style sheet then the choice is yours, but the most common usage for inline citations would be not to repeat the name, while leaving the sentence readable with the parenthetical part left out, i.e.

As shown in Tyndall (1869), the sky is blue.

This is specifically when the name is reused, so it would still be

As shown in another paper (Tyndall, 1869), the sky is blue.

Answer 2

It's obviously context dependent and depends on what you want to emphasize. You can either call attention to the author or the paper. If there is a reason to prefer one to the other do so. For example, if you are tracing a line of work over several studies, perhaps attention on the author as the common thread and the paper as just an instance makes more sense.

"Initial observations by Tyndall [1], established the sky was colored. Later, with more precise gazing at the sky, Guest [2] established it was blue."

Conversely, if you are discussing a raft of papers from different authors supporting a common idea, emphasis on the papers makes more sense.

"Gas colors observation has been reviewed [1-7]."

I would think in many general cases, either choice is fine and it is just an issue of the turn of phrase. After all, you have the paper citation either way. It's just a question of how you like to structure your narrative. And unlikely that one way will be strongly wrong.