Speech Rate Estimates, Language of Schooling and Bilingual Digit Span

Abstract

Bilinguals obtain larger digit spans in the language in which speech rate is fastest. This effect is generally interpreted as support for a central tenet of working memory theory, which proposes subvocal rehearsal rate as an influential determinant of memory span. Variation in the method of speech rate estimation, however, has been high, making comparison between studies difficult. In the present study, we compared the predictive power of three estimates of speech rate in relation to auditory digit span for two distinct bilingual types across nine school grades (1–9). One type spoke Swedish in the home and school (SS), the other spoke Finnish in the home and Swedish at school (FS). The results showed SS consistently obtained faster speech rates in Swedish, whereas FS obtained shorter articulation and numeral reading times in Swedish, as did grades 1–3 on a digit word reading task. However, FS grades 4–9 obtained equivalent digit word reading times between the languages. SS obtained a larger digit span in Swedish than Finnish, whereas FS obtained an equivalent digit span between the languages. Thus the results indicated that memory span was mediated by factors other than phonological loop functioning, as articulation time did not predict memory span performance for FS. The finding that FS obtained lower digit spans in Swedish relative to SS suggested that the former were disadvantaged in the processing of digits compared to native speakers of the language of schooling.