Research paper writing: how do you know when you've found "enough" sources?

[AdamWolf]

I'm in the middle of a research paper for my developmental psych class and I have a question for the seasoned pros here:

How many sources is enough???

I swear, every time I think I'm done finding articles, I find ONE MORE that contradicts something or adds a new angle and suddenly I'm back in the database spiral. I start on PubMed, then I'm on PsycINFO, then Google Scholar, then oh look a citation in someone's paper leads me somewhere else... and suddenly it's 3am and I've read 40 abstracts and retained approximately none of them.

My professor said "comprehensive but not exhaustive" which is the most unhelpful thing anyone has ever said to me. What does that MEAN in real numbers?? Is 15 good? 20? 30?? I'm studying attachment theory and there's like 80 years of research, I can't read it ALL.

I think part of my problem is I get anxious about missing something important. Like what if the ONE article I skip has the exact finding that would make my whole paper better? What if my professor knows about it and thinks I'm sloppy??

For those of you who do a lot of research paper writing: how do you know when to STOP looking for sources and just WRITE already?? I need a system. A cutoff rule. Anything.

 

[Angelika]

Here's my practical rule: when you're seeing the SAME studies cited over and over in different papers, you've found the core literature. If you have those key studies, plus a few recent ones (last 5 years) to show you're current, you're good.

For a typical undergrad psych paper, 15-20 quality sources is usually plenty. Quality matters more than quantity—a few really relevant articles beat 40 tangentially related ones.

Also, your professor probably has a few key papers they love. Check their publications if they're in the field! Easy brownie points