Duck test is a humorous term for a form of inductive reasoning. This is its usual expression: If it looks like a duck, swims like a duck, and quacks like a duck, then it probably is a duck. The test implies that a person can identify an unknown subject by observing that subject's habitual characteristics. It is sometimes used to counter abstruse, or even valid, arguments that something is not what it appears to be. == HistoryEdit == Indiana poet James Whitcomb Riley (1849–1916) may have coined the phrase when he wrote: When I see a bird that walks like a duck and swims like a duck and quacks...