People say "background" here, because the default assumption is HN readers have software expertise, but it's frequently unclear what else, if anything, they have here.

I do agree "background" is vague, but I generally assume the minimal threshold to say that is something like a previous career, undergraduate degree, or graduate degree in the background. I personally wouldn't say I had a background in something I was only an amateur enthusiast of.

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That being said, what on earth gives you the idea a substantial background in sociology WOULDN'T be relevant here?