Don: Time to go again to the A Moment of Science mailbag. A listener writers: Dear Ya?l and Don: Why is it that whenever I see someone looking at something, like someone gazing up at the sky, I look there too? Is it just me, or do we all do this? Ya?l: Great question! And the answer is that what scientists call gaze-following is pretty much a universal human trait. We're all prone to follow another person's gaze even if we're not sure what they're looking at, or why. D: Right. But why do we gaze-follow? British researchers think it dates back to our primitive primate ancestors, who may have evolved the behavior as a way to locate food. When the British scientists studied gaze-following in lemurs, which are very primitive primates, they found that lemurs do in fact use gaze-following as a strategy to locate areas likely to contain food. When a lemur sees one or more of its fellows looking in a particular direction, it will turn its attention that way, too. And at some point the lemur is likely to search that area for hidden food. Y: Of course, gaze-following could also be a way of sensing danger and staying away from a certain place. In any case, the point is that our human tendency to gaze-follow could have ancient origins. We no longer follow gazes for foraging purposes. But it's still useful as a way of being alerted to something interesting, or menacing, in the vicinity.