Add to ORKGIn this contribution, the authors intend to offer an interesting exemplification of the kind of positive interaction that may arise between acquisition studies and linguistic theory. Starting from a full range of comparative studies showing the presence of a delay in the acquisition of the interpretive properties of non-reflexive pronominals and the absence of such a delay in languages where clitic pronominals are involved, the authors argue that this range of effects is elegantly derived from a general constraint on extra-lexical operations of valency reduction, turning relations into one-place predicates. The analysis leads to a sort of cross-modular (re)interpretation of Principle B of Binding Theory and to a radically new analysis of th...