Semantics and phonology constrain compound formation

Berent and Pinker (2007) presented five experiments concerning the formation of compounds, especially the apparent restriction on the occurrence of "regular" plurals as modifiers (as in *RATS-EATER). Their data were said to support a "words and rules" approach to inflectional morphology, and to contradict the approach developed by Haskell, MacDonald, and Seidenberg (2003) in which multiple probabilistic constraints, mainly involving semantic and phonological properties of words, determine degree of acceptability. We examine Berent and Pinker's studies and show that a) their experiments tested hypotheses that are incorrectly ascribed to our theory, and b) their data are actually compatible with our account. Contrary to the words and rules approach, there are phonological effects on modifier acceptability that cannot be subsumed by a grammatical rule.