Chinese and English speakers seem to hold different conceptions of time which may be related to the different codings of time in the two languages. Employing a sentence–picture matching task, we have investigated this linguistic relativity in Chinese–English bilinguals varying in English proficiency and found that those with high proficiency performed differently from those with low proficiency. Additional monolingual English data, reported here, showed further that high-proficiency bilinguals performed similarly to the English monolinguals, suggesting that Chinese speakers’ sensitivity to the time of an action event might be modifiable according to the extent of their experience with a tensed language.

This article aims at revitalizing the debate concerning the measurement of language proficiency (LP) in the study of bilingualism (Grosjean, 1998). A review is presented of the way in which LP was measured in a corpus of 140 empirical papers published in volumes 1–14 (1998–2011) of the journal Bilingualism: Language and Cognition. In 55% of these papers, in which the assessment of LP as an independent or moderating variable was a necessary or preferred requirement, LP was not measured with an objective LP test. Seldom were participants’ LP scores used in explaining variance obtained in the dependent variable(s). After the discussion of some unresolved problems concerning cross-language comparisons of LP in bilinguals’ languages, recommendations are offered for the measurement of LP. One of the recommendations is that, in studies investigating between-group contrasts, researchers carefully consider the assessment of participants’ proficiency in the language(s) concerned, even in native-speaker comparison groups.