Language-specific effects in Alzheimer's disease: Subject omission in Italian and English

The aim of this study was to verify whether the repetition abilities in Alzheimer patients interact with the linguistic properties of individual languages, such that speakers will omit nominal referents more often only if the omission is a grammatical option in their language. Unlike English, where an overt nominal referent is always required in grammatical subject position, Italian allows grammatical subjects to be unexpressed. In Experiment 1, twelve Italian speakers with Alzheimer's disease (AD) and twelve age- and education-matched controls repeated sentences of varying length and complexity. As predicted, Italian AD speakers omitted sentence subjects in complex sentences while control participants very rarely did. In Experiment 2, ten English AD speakers, matched with the Italian AD participants with respect to age and severity of the disease, and ten age- and education-matched controls repeated translation equivalent materials. Unlike the Italian AD participants, English AD participants did not omit sentence subjects. Italian and English AD participants, however, were comparable in their global ability to repeat sentences of varying length. Together these results indicate that the performance of AD speakers in repeating sentences interacts with language-specific properties.