Consider this image,
Look at the lady on the right. Of course, she has a cute smile, but notice that she is looking up at you.
From what I can tell, this makes the women more attractive to the fellas. Perhaps it emphasizes a subservient position, which makes the fella feel more comfortable. Contrast that image to this,
Or maybe this,
Do you, as a fella, feel comfortable? Notice that she is not looking up at you. Probably if you deal with her, you will be in for rough ride, or maybe suicide.
Still, there seems to be a pre-disposition in men toward having a positive vibe toward women who look up at them. Pro tip to women — in online dating pictures, look up, not straight, or down.
Exit question — Have you experienced this phenomenon?