How to not use Face naming to help detect further faces?

HI,

My question may sound funny.

My understanding is both iPhoto and Aperture use detected face in helping detect other faces. That's what the help suggest, in identifying more face it facilitate the detection.

In many photo you would have someone visible and would want to identify her/him. by doing so I would use anything but the face, the back of the head or other part of the body that is visible.

If Aperture/iPhoto would then use that added image to improve face detection with nothing useful, it would make it even less efficient!

Are their other way to identify someone and have it in the Faces without affecting the faces definition the the software seem to be building? tag not to use the face for further detection for example.

Vincent