Happy dogs are easy to spot. Their tails wag excitedly back and forth, they cover us in sloppy, wet kisses and, sometimes, their whole body shakes with enthusiasm as they roll over on their backs, ...

Tears are a normal response to moments of pain, grief, and sadness. But it’s also not uncommon to find people sniffling into their handkerchiefs on happy occasions, such as weddings, graduations, or ...