Oh, I do love parsimony (specifically, the one related to Occum’s razor).
If there is anything that you take away from a psychology degree be it the rule of parsimony.
Unfortunately, hardly anyone ever mentions it in undergraduate degrees these days. Probably because if they did then students would realise that biological psychology is unfit for purpose.
Friends and family arguing some bullshit theory? Take a pair of parsimony scissors to it.
And, if you really want a first class mark in your exam, evaluate theories using parsimony. Just mentioning parsimony these days will probably get you a first.
I’m not going to actually define the rule here because someone will inevitably complain about the latin translation that I use. But, if you can’t be arsed to google it, and want a crash course in it and an entertaining story, go watch Carl Sagan’s “Contact” with Jodie Foster. After you’ve seen that, I guarantee you’ll want to google it.