Talking birds do not dissect the sounds of their imitations into discrete units. Polly and Molly do not rhyme for a parrot. They are as different as hello and good-bye. One property of all human languages (which will be discussed further in chapter 6) is the discreteness of the speech or gestural units, which are ordered and reordered, combined and split apart. Generally, a parrot says what it is taught, or what it hears, and no more. If Polly learns "Polly wants a cracker" and "Polly wants a doughnut" and also learns to imitate the single words whiskey and bagel, she will not spontaneously produce, as children do, "Polly wants whiskey" or "Polly wants a bagel" or "Polly wants whiskey and a bagel." If she learns cat and cats, and dog and dogs, and then learns the word parrot,she will be unable to form the plural parrots as children do by the age of three; or can a parrot form an unlimited set of utterances from a finite set of units, or understand utterances never heard before.