Inflectional morphology: evidence for an advantage of bilingualism in dyslexia

If science were a game, a dominant rule would probably be to collect results that are statistically significant. Several reviews of the psychological literature have shown that around 96% of papers involving the use of null hypothesis significance testing report significant outcomes for their main results but that the typical studies are insufficiently powerful for such a track record. We explain this paradox by showing that the use of several small underpowered samples often represents a more efficient research strategy (in terms of finding p < .05) than does the use of one larger (more powerful) sample. Publication bias and the most efficient strategy lead to inflated effects and high rates of false positives, especially when researchers also resorted to questionable research practices, such as adding participants after intermediate testing. We provide simulations that highlight the severity of such biases in meta-analyses. We consider 13 meta-analyses covering 281 primary studies in various fields of psychology and find indications of biases and/or an excess of significant results in seven. These results highlight the need for sufficiently powerful replications and changes in journal policies.

A total of 104 six-year-old children belonging to 4 groups (English monolinguals, Chinese-English bilinguals, French-English bilinguals, Spanish-English bilinguals) were compared on 3 verbal tasks and 1 nonverbal executive control task to examine the generality of the bilingual effects on development. Bilingual groups differed in degree of similarity between languages, cultural background, and language of schooling. On the executive control task, all bilingual groups performed similarly and exceeded monolinguals; on the language tasks the best performance was achieved by bilingual children whose language of instruction was the same as the language of testing and whose languages had more overlap. Thus, executive control outcomes for bilingual children are general but performance on verbal tasks is specific to factors in the bilingual experience. © 2012 The Authors. Child Development © 2012 Society for Research in Child Development, Inc.