Mental variables are central to symbolic accounts of cognition. Conversely, according to the pattern associator hypothesis, variables are obsolete. We examine the representation of variables by investigating the Obligatory Contour Principle (OCP, McCarthy, 1986) in Hebrew. The OCP constrains gemination in Hebrew roots. Gemination is well formed at the root's end (e.g., SMM), but not in its beginning (e.g., SSM). Roots and geminates, however, are variables; hence, according to the pattern associator view, the OCP is unrepresentable. Three experiments demonstrate that speakers are sensitive to the presence of root gemination and constrain its location. In forming words from novel biconsonantal roots, speakers prefer to reduplicate the root's final over its initial radical, and they rate such outputs as more acceptable. The avoidance or rejection of root-initial gemination is independent of its position in the word and is inexplicable by the statistical frequency of root tokens. Our results suggest that linguistic representations specify variables. Speakers' competence, however, is governed by violable constraints.