Thank You, Scientists

So, I have to wonder which I look like:

Whether you are looking for a long-term relationship or just a one-night stand may be written on your face for others to read, say researchers from Durham University (England), St. Andrews University (Scotland) and Aberdeen University (Scotland).

OK, quick, guess which is which:

That's right, one on the left: one-night stand. And on the right: one-night stand.

OK, How about these:

Very good, on the left: long-term relationship, and help with her chemistry homework. And on the right: long-term relationship, and starter repair on her Volvo.