What is the reference standard for a substance that is subjectively dopaminergic?

We often hear people saying that such-and-such nootropic "feels dopaminergic".

I am wondering, what does it mean for something to feel dopaminergic? How does dopamine feel?

How are we distinguishing this characterization? Do people base it off of the effects of dopamine that they read on wiki / textbook definitions,

OR

is there some substance that produces effects which are purely dopaminergic and we then compare noots to that drug?

You know what I'm saying, right. Sorry if I can't explain it well, but I'm basically asking what the effects of "pure dopamine" are and which substance is the reference standard that produces these effects (if applicable).

Or are we simply comparing the noot to what we guess how dopaminergic effects are to be perceived based on (animal) studies of targeted receptor activation and the subsequent behavioral manifestations that are observed? Thanks