Matt,
that's interesting. If you read Alan Pease's books about the physiological differences between men and women, he tells us that the reason why a bloke often can't find something in the fridge is that their power of (visual) concentration is sort of tunnel-like in it's projection. So in other words, we have to scan everywhere, - left to right and up and down to make sure we've covered the whole area.
Whereas when you call your wife to come and take a look, her visual power of concentration can take in a much larger area at once, so she doesn't need to scan like we do.
So that would explain why they can spot us perving, but we don't see them doing it.
