In morphology, the type frequencies of the different patterns in existing forms have a considerable influence in the way speakers create new forms, i.e., on the productivity of those patterns. However, type frequencies are sometimes insufficient to fully account for the productivity, or lack thereof, of some morphological patterns. This raises the question of which other factors may play a role in the abstraction and updating of the representations that guide morphological productivity. This thesis addresses this question by exploring linguistic situations in which the influence of the type frequencies is limited by a low number of existing forms and/or may conflict with the new input speakers encounter in an interaction.
Our results show that the type frequencies indeed play a major role in the way speakers create novel forms. However, speakers sometimes fail to abstract a pattern when the number of existing forms is too low. In this situation, certain patterns are over- or under-represented in novel forms as compared to their type frequencies among existing forms. The presence of preferences which are unmotivated by type frequencies suggests that speakers have inherent biases towards certain patterns.
Besides, speakers are able to quickly converge with an interaction partner, even when this goes against the tendencies observed in existing forms. Thus, it follows that speakers can gradually modify their preferences through the accumulated effect of morphological convergence in multiple interactions. Consequently, these findings suggest an important role for convergence in the emergence and evolution of morphological patterns.