It is what biologists call "fubsy." The theory has it that we, as humans, are hardwired to protect our progeny, and as a result we are also instinctively protective of creatures that possess attributes common to human infants. Clumsy animals, preferably chubby ones with large eyes, big heads, and short limbs, are said to be fubsy.

The human cuteness detector is set at such a low bar, researchers said, that it sweeps in and deems cute practically anything remotely resembling a human baby or a part thereof, and so ends up including the young of virtually every mammalian species, fuzzy-headed birds like Japanese cranes, woolly bear caterpillars, a bobbing balloon, a big round rock stacked on a smaller rock, a colon, a hyphen and a close parenthesis typed in succession.