When someone interesting enters your view, you give them a serious look. Then you notice the person or some others nearby have noticed you staring. So you immediately look around at others in your view so the noticers think that you are not stairing but instead looking equally at everyone nearby. A little like the Package Peakin Wiener Gazer (but not much).
Look at Jeff. He was eyeing that hottie that's way out of his league and now he's doing a few followup glances at others to hide his foolery.