Babies learn rules (Marcus, Vijayan, Bandi Rao and Vishton).

• Seven-month-olds were presented with 16 "sentences", each consisting of 3 1-syllable "words". All sentences presented to a given baby followed a particular "rule": AAB, ABB, or ABA.

  AAB: le le di, le le je, le le li, le le we, wi wi di, wi wi je, ...

  ABB: le di di, le je je, le li li, le we we, wi di di, wi je je, ...

  ABA: le di le, le je le, le li le, le we le, wi di wi, wi je wi, ...

• Tested later on sentences consisting of syllables which did not appear in the training set, babies clearly distinguished sentences which obeyed the training rule from those which did not (they showed a preference for the "ungrammatical" sentences).

  (trained on ABB)

  ba po po -> YES
  ko ga ga -> YES
  ba po ba -> NO
  ko ga ko -> NO