The structure of the brain and the nature of evolution suggest that, despite its uniqueness, language likely depends on brain systems that also subserve other functions. The declarative / procedural model claims that the mental lexicon of memorized word- specific knowledge depends on the largely temporal-lobe substrates of declarative memory, which underlies the storage and use of knowledge of facts and events. The mental grammar, which subserves the rule-governed combination of lexical items into complex representations, depends on a distinct neural (...) system. This system, which is composed of a network of specific frontal, basal - ganglia, parietal and cerebellar structures, underlies procedural memory, which supports the learning and execution of motor and cognitive skills, especially those involving sequences. The functions of the two brain systems, together with their anatomical, physiological and biochemical substrates, lead to specific claims and predictions regarding their roles in language. These predictions are compared with those of other neurocognitive models of language. Empirical evidence is presented from neuroimaging studies of normal language processing, and from developmental and adult- onset disorders. It is argued that this evidence supports the DP model. It is additionally proposed that “ language ” disorders, such as specific language impairment and non-fluent and fluent aphasia, may be profitably viewed as impairments primarily affecting one or the other brain system. Overall, the data suggest a new neurocognitive framework for the study of lexicon and grammar. (shrink)

As adults age, their performance on many psychometric tests changes systematically, a finding that is widely taken to reveal that cognitive information-processing capacities decline across adulthood. Contrary to this, we suggest that older adults'; changing performance reflects memory search demands, which escalate as experience grows. A series of simulations show how the performance patterns observed across adulthood emerge naturally in learning models as they acquire knowledge. The simulations correctly identify greater variation in the cognitive performance of older adults, and successfully (...) predict that older adults will show greater sensitivity to fine-grained differences in the properties of test stimuli than younger adults. Our results indicate that older adults'; performance on cognitive tests reflects the predictable consequences of learning on information-processing, and not cognitive decline. We consider the implications of this for our scientific and cultural understanding of aging. (shrink)

Many generativist accounts argue for very early knowledge of inflection on the basis of very low rates of person/number marking errors in young children's speech. However, studies of Spanish and Brazilian Portuguese have revealed that these low overall error rates actually hide important differences across the verb paradigm. The present study investigated children's production of person/number marked verbs by eliciting present tense verb forms from 82 native Finnish-speaking children aged 2;2–4;8 years. Four main findings were observed: Rates of person/number marking (...) errors were higher in low-frequency person/number contexts, even excluding children who showed no evidence of having learned the relevant morpheme, most errors involved the use of higher frequency forms in lower frequency person/number contexts, error rates were predicted not only by the frequency of person/number contexts but also by the frequency of individual “ready-inflected” lexical target forms, and for low-frequency verbs, lower error rates were observed for verbs with high phonological neighborhood density. It is concluded that any successful account of the development of verb inflection will need to incorporate both rote-storage and retrieval of individual inflected forms and phonological analogy across them. (shrink)

This study adjudicates between two opposing accounts of morphological productivity, using English past-tense as its test case. The single-route model posits that both regular and irregular past-tense forms are generated by analogy across stored exemplars in associative memory. In contrast, the dual-route model posits that regular inflection requires use of a formal “add -ed” rule that does not require analogy across regular past-tense forms. Children saw animations of an animal performing a novel action described with a novel verb. Past-tense forms (...) of novel verbs were elicited by prompting the child to describe what the animal “did yesterday.” Collapsing across age group, the likelihood of a verb being produced in regular past-tense form was positively associated with the verb's similarity to existing regular verbs, consistent with the single-route model only. Results indicate that children's acquisition of the English past-tense is best explained by a single-route analogical mechanism that does not incorporate a role for formal rules. (shrink)