Psychologists have become wary of stating: "The human being is the only animal that… " Monkeys keep proving them wrong. But don't place all bets on primates; there's a whole kingdom of counterexamples out there.
Talk to the Hand
Among chimps and bonobos, a hand gesture can have multiple meanings ("help me out," "give me food"), whereas a shriek or grunt usually has just one. That apes use gestures more flexibly than they use sounds supports the emerging theory that human language—the ultimate Swiss army knife—evolved from basic signing.
Birdbrain No More
When researchers asked a middle-aged parrot to describe an empty tray during a counting test, the bird spontaneously answered, "none." Understanding the abstract concept of zero is quite a hoop to fly through; humans can't do it until age 3 or 4.
Funny Farm
Laughter is older than language. Neuroscientists have shown that when tickled playfully, even the lowly rat will emit high-pitched chirps—an analog to a human chuckle.
