Implementing the U-shaped curve in Distributed Morphology and as a by-product of the third factor

Abstract

In this paper, we present a novel formal approach to overregularisation (e.g. fazi “doed”, trazi “bringed”) in Brazilian Portuguese (BP), a phenomenon widely attested in children’s production. Three previous accounts for this phenomenon are also reviewed and at least partially rejected. The first explained overregularisation on the basis of Minimize Exponence (an economy principle in Distributed Morphology) not being followed by children; the second achieved the same goal by positing constraint ranking (a main feature in Optimality Theory) that is faulty in children’s grammar when compared to adult knowledge; and the third analyses BP through the framework of Grammar Competition. Our main departures with these approaches are that the first two a) are dependent on children’s breaking of the theoretical principles just mentioned; b) no learning mechanism is ever discussed to justify this; c) although both describe a system that indeed produces overregularised forms, they fail to predict or capture the three stages of the U-shaped curve, being an explanation solely of its dipping section and not of children’s development; and that the third d) only deals with noise but not exceptions, the main point of the overregularisation process. In an attempt to remedy those perceived flaws, our approach keeps theoretical principles intact, maintaining parity with adult competence and addressing points a) and b). Furthermore, we integrate the chosen descriptive toolkit of Distributed Morphology and general cognitive biases/abilities in the form of Biberauer’s Minimise Maximise Means and Yang’s Tolerance Principle (TP) in order to explain the developmental path of BP acquisition takes throughout the U-curve, thus addressing points c) and d). Finally, we argue that our proposal is naturally compatible with the notion of grammar competition by virtue of assuming TP, which might explain why children do not categorically overregularise irregular verbs, but rather do so at a given rate.