ABSTRACT
Babies discover morphemes early, but with some interesting differences from adult morphology. They appear to apply exclusivity: Inflectional morphemes are uniquely associated with a lexical category (e.g. only nouns may end in -s), and infants initially do not allow allomorphs (e.g. the inflection -s is always voiceless, even if the voiced variant is more frequent in the child-directed speech they hear). Young children’s morphology is also different in that they systematically aim for harmony across syllables (consonant harmony, vowel harmony), to the point of reduplication. Since it is not possible to correct children’s morphology (correction being ‘negative evidence’), adults prefer to model correct forms (‘positive evidence’), and children’s books make morphemes salient by repeating them, playfully overextending or misusing them, or even by inventing new ones. To trigger surprise, these morphological outliers must be playful and masterful; imitating children’s morphology is counterproductive because such caricatures fail to surprise and come at the expense of safe and cooperative trust.
