A recent study by Japanese researchers observing that dogs cry happy tears when reuniting with their guardians should surprise no one. Science long ago proved that dogs, like all animals, experience a full range of emotions, including joy, sorrow, empathy, grief and doubt. The evidence is both academic and empirical.
Elephants repeatedly return to the graves of deceased loved ones to pay their respects. Rats giggle when they’re tickled. Crows hold grudges when they see others who have offended them — even years later.
Captive rhesus monkeys refused to pull a switch to obtain food if it meant another monkey would receive a shock — even when they were hungry. And when given the choice between feasting on chocolate or saving a drowning companion, rats chose the latter.