Frequency as a Barrier to Learning Complex Nominal Morphology

Most languages with highly structed morphological systems show some degree of syncretism, where the same affix is used for multiple categories. The typology of syncretism has suggested that syncretism is most likely to occur for structurally and semantically marked categories. In two artificial grammar learning experiments, English-speaking adults were exposed to a 3-gender x 3-number nominal system, where one number category (Singular, Dual, or Plural) showed syncretism across gender. In the experiment, the frequency of the syncretic morpheme was equal to non-syncretic morphemes, but there were 3x fewer items containing the syncretic morpheme. Participants failed to learn the syncretic morpheme, with no biases for marked categories. These results suggest that low frequency of syncretic items significantly impairs learning syncretic categories. Suggestions for design