Instinct & Beauty
One's opinion of beauty may be influenced very early but beauty is looked upon with interest by even infants. Infants who don't know what ideal weights or symmetric faces are. Infants will gaze upon a symmetrical face longer than an asymmetrical one. Even if that face is not of its mother or father. Children often stare at beautiful women and mimic their moves -- even showing favoritism towards more attractive individuals.
Children didn't learn it from their parents, it is instinctive. They aren't born knowing the Silver Chin Soft Tissue Assessment or Ideal Cheek placement. Infants are just born knowing what pleases the eye.
Even in the animal kingdom the preferences are around who has the best plumes, mane or horns. Even mother birds will tend to feed the most brightly colored of their offspring first, fearing the others may be sick so more energy is spent on the pretty, healthy ones.
Even the lioness will choose the stronger, more attractive males to contribute their genes. Each species chooses the best of the group to produce their offspring with the best chance to survive and prosper. So, why all this favoritism? I know, we are not animals nor are we infants, but I am trying to point out that no matter how we are brought up our eye favors the showier, shinier, newer model. It is instilled within our very core.
Beauty is not an exact science, but according to some Plastic Surgeons there is a specific proportion system that the ideal face tends to hover at. This includes facial height, width and symmetry. First the face is evaluated from its frontal view and then its lateral (side view). There are steps that can determine the facial lateral width or projection (as in your profile) and there is the oblique assessment for contours such as the cheek bones, chin and nose.
So what measurement system are we going by? Well there isn't really a measurement system that dictates who is attractive and who is not, it's more of what university professors, artists and plastic surgeons deem "ideal" Where this may seem grossly unfair, it does have fact to it regarding what pleases the eye. What pleases the idea on a large scale tends to amount to about the same measurements of the facial features in proportion to each other. For instance the eyes in relation to the nose, the nose in relation to the mouth, the mouth in relation to the chin and so on and so forth.
Scientists say that the preference for symmetry is a highly evolved trait seen in many different animals. Female swallows, for example, prefer males with longer and more symmetric tails, while female zebra finches mate with males with symmetrically colored leg bands.