The signal and the noise

Studies on the effect of bilingualism on executive functioning have sometimes failed to find significant differences between performance of monolingual and bilingual young adults. This paper examines the interpretation of these null findings and considers the role of three factors: definition of bilingualism, appropriateness of statistical procedures and interpretations, and the range of data considered. The conclusion is that a correct interpretation of this important issue will require careful consideration of all the data and scrupulous attention to design details.