Compound formation is constrained by morphology

Why do compounds containing regular plurals, such as rats-infested, sound so much worse than corresponding compounds containing irregular plurals, such as mice-infested? Berent and Pinker (2007) reported five experiments showing that this theoretically important effect hinges on the morphological structure of the plurals, not their phonological properties, as had been claimed by Haskell, MacDonald, and Seidenberg (2003). In this note we reply to a critique by these authors. We show that the connectionist model they invoke to explain the data has nothing to do with compounding but exploits fortuitous properties of adjectives, and that our experimental results disconfirm explicit predictions the authors had made. We also present new analyses which answer the authors’ methodological objections. We conclude that the interaction of compounding with regularity is a robust effect, unconfounded with phonology or semantics.