This squib proposes to extend the traditional taxonomy of pairwise process interactions (which contains “feeding,” “bleeding,” “counterfeeding,” and “counterbleeding”) to include the classes “shifting” and “countershifting.” A process “shifts” another if it does not feed or bleed it but rather causes it to apply in a different way. “Countershifting” is the opaque counterfactual inverse of shifting, and it fills a terminological gap identified by Kiparsky (2015) . The class of countershifting interactions is claimed to be theoretically significant: Harmonic Serialism is able to apply the opaque process in countershifting interactions but generally not in counterfeeding or counterbleeding.

We develop an evaluation metric for Optimality Theory that allows a learner to induce a lexicon and a phonological grammar from unanalyzed surface forms. We wish to model aspects of knowledge such as the English-speaking child’s knowledge that the aspiration of the first segment of k h æt is predictable and the French-speaking child’s knowledge that the final l of table ‘table’ is optional and can be deleted while that of parle ‘speak’ cannot. We show that the learner we present succeeds in obtaining this kind of knowledge and is better equipped to do so than other existing learners in the literature.