They Know . . .

If you’re cheating on your spouse, New York Magazine reports, do yourself a favor and avoid buying gifts at Tiffany’s. The sales help — and the private investigators who are trailing you — know what you’re up to:

“What drives the whole holiday thing is diversion of assets,” says Michael McKeever, another P.I. “Think of it like caveman days. You suspect your husband is out banging some broad. Then he comes home from hunting with only half a yak. You got to wonder, Where’s the other half of that yak going?”

In New York these days, that proverbial yak carcass often comes inside a powdery blue Tiffany’s bag. Although cheaters can purchase gifts at several stores for both their lovers — or more — private eyes are pressed to remember a Christmas they didn’t spend staking out the store’s jewelry cases. Salespeople there know what’s up. “Typically,” says one clerk, the two-timer goes for “pieces that go wow! Pieces that try to recapture a certain spark.” Simple solitary diamond pendants (about $2,000) are also popular. The smarter ones pay for their gifts with company credit cards or cash.