1. At a time of mass visual communication, young male students are bound to be strongly influenced by the images which daily bombard them. This has more to do with fashion than evolution.
2. The face and head, masked in the experiments, are almost certain to be of great significance in mating choice, indicating - through eyes, skin, bone structure, symmetry - health, energy, emotional character and other qualities of "reproductive potential".
I suspect, however, that lost in the mists of evolutionary time is the likelihood that women were the primary choosers, having much more to lose if they ended up with a reproductive duffer.