Spoiler alert: None of us know what we are doing when it comes to romance according to science. Or, at least, we think so. At least some of us are bad at romance. See, these are all pretty much for heterosexual relationships, since the science surrounding any other kind of attraction is shockingly nonexistent. Because we know science won't apologize, like the jerk that it is, we apologize to a lot of our fanbase out there who won't find this information useful.
(As always, thanks to AuntieMeme for the voodoo she works putting these together.)