Me and my complicated or so gf were talking the other, shes a waitress at Taco Mac in the PTC.

GF: She was complaining, that, damn, I need my nails done.
Me: why? their gonna get fucked at work and shit
GF: I'll make more tips with my nails done
Me: a dude is gonna tip you more b/c you have a french manicure?
GF: yes

please explain?

All the times I've ever eaten at a restaurant, I've never actively looked at a waitress and have been, damn, she has nice nails, I'm gonna tip her better.

or is there some "scientific" study that states this? that men unconciously tip well to women, based on underlying characteristics such as nails, perfume, clothing, etc.

Personally, I tip well if she/he is doing their job and are good at it and it does help if shes a looker and atleast "talks" to you