Homophony avoidance has often been claimed to be a mechanism of language change. We investigate this mechanism in Dutch by applying two strands of research – corpus studies and experimental data – to find support for claims based on earlier historical observations. Throughout the history of Dutch, homophony avoidance has been named as the cause of language change or inhibition of change on several occasions. We build on these historical observations with an experimental study and a corpus study on a synchronic Dutch alternation, where avoidance of homophony between present and past tense can appear. Plurals of verbs with a stem ending in a dental show homophony with the present when they are used in the preterite (compare zetten ‘put’ pst-pl with zetten ‘put’ prs-pl). This homophony can be avoided by using the perfectum (hebben gezet ‘have put’). A wug-style experiment shows that verbs with dental stem are indeed used significantly more in the perfectum in the plural than in the singular, while verbs without dental stem do not show this difference. A corpus study on Dutch further corroborates these results. Combined, these studies make a strong case for homophony avoidance as a plausible mechanism of language change.

We investigated whether children's inhibitory control (IC) is associated with their ability to produce irregular past tense verb forms as well as learn from corrective feedback following overregularization errors. Forty-eight 3;6 to 4;5 year old children were tested on the irregular past tense and provided with adult corrective input via models of correct use or recasts of errors following ungrammatical responses. IC was assessed with a three-item battery of tasks that required suppressing a prepotent response in favor of a non-canonical one. Results showed that IC was associated with children's initial production of irregular forms, but not associated with their post-feedback production. Findings are discussed in terms of current theories of past tense use and acquisition.

This paper explores whether the poor mastery of morphosyntax exhibited by second language (L2) learners can be tied to difficulties with non-syntactic processing. Specifically, we examine whether problems with English regular and irregular past tense are related to poor L2 phonological ability and lexical access, respectively. In Experiment 1, L2 learners showed poorer past tense mastery than native English speakers in grammaticality judgment and production tasks. L2 phonological ability was positively correlated with correct performance on regular verbs and negatively with unmarked production. L2 lexical access was positively correlated with correct performance on irregular verbs, and negatively with overregularization production. Experiment 2 simulated these difficulties in native English speakers by placing them under phonological processing (noise) or lexical access (deadline) stress. Noise selectively impacted regular verbs in grammaticality judgment but impacted all verb types in production. Deadline pressure impacted irregular verbs while sparing regular verbs across both tasks. Thus, non-syntactic processing difficulties can have specific impacts on morphosyntactic performance in both non-native and native English speakers.

It is often assumed that similar domain-specific behavioural impairments found in cases of adult brain damage and developmental disorders correspond to similar underlying causes, and can serve as convergent evidence for the modular structure of the normal adult cognitive system. We argue that this correspondence is contingent on an unsupported assumption that atypical development can produce selective deficits while the rest of the system develops normally (Residual Normality), and that this assumption tends to bias data collection in the field. Based on a review of connectionist models of acquired and developmental disorders in the domains of reading and past tense, as well as on new simulations, we explore the computational viability of Residual Normality and the potential role of development in producing behavioural deficits. Simulations demonstrate that damage to a developmental model can produce very different effects depending on whether it occurs prior to or following the training process. Because developmental disorders typically involve damage prior to learning, we conclude that the developmental process is a key component of the explanation of endstate impairments in such disorders. Further simulations demonstrate that in simple connectionist learning systems, the assumption of Residual Normality is undermined by processes of compensation or alteration elsewhere in the system. We outline the precise computational conditions required for Residual Normality to hold in development, and suggest that in many cases it is an unlikely hypothesis. We conclude that in developmental disorders, inferences from behavioural deficits to underlying structure crucially depend on developmental conditions, and that the process of ontogenetic development cannot be ignored in constructing models of developmental disorders.