Pii: S0010-0277(01)00167-6

Does the productive use of language stem from the manipulation of mental variables (e.g. “noun”, “any consonant”)? If linguistic constraints appeal to variables, rather than instances (e.g. “dog”, “m”), then they should generalize to any representable novel instance, including instances that fall beyond the phonological space of a language. We test this prediction by investigating a constraint on the structure of Hebrew roots. Hebrew frequently exhibits geminates (e.g. ss) in its roots, but it strictly constraints their location: geminates are frequent at the end of the root (e.g. mss), but rare at its beginning (e.g. ssm). Symbolic accounts capture the ban on root-initial geminates as *XXY, where X and Y are variables that stand for any two distinct consonants. If the constraint on root structure appeals to the identity of abstract variables, then speakers should be able to extend it to root geminates with foreign phonemes, including phonemes with foreign feature values. We present findings from three experiments supporting this prediction. These results suggest that a complete account of linguistic processing must incorporate mechanisms for generalization outside the representational space of trained items. Mentally-represented variables would allow speakers to make such generalizations. q 2002 Elsevier Science B.V. All rights reserved.