During three years as a researcher at the Centro de Estudios Puertorriqueños, City University of New York, her studies of code-switching among Puerto Ricans in New YorkPoplack, Shana (1980) Sometimes I'll start a sentence in Spanish y termino en español: toward a typology of code-switching. Linguistics 18: 581–618. initiated her characterization of universal patterns of intrasentential language mixing, and demonstrated that fluent code-mixing is a bilingual skill rather than a defect. Over three decades, she made numerous contributions to the understanding of bilingual syntax in social context, many involving typologically contrasting language pairs.Poplack, Shana (2004) Code-Switching. In Ammon, U., N. Dittmar, K.J. Mattheier and P. Trudgill (eds), Sociolinguistics. An International Handbook of the Science of Language and Society. Berlin: Walter de Gruyter. 2nd edition.589-596. Recent projects (2008) focus on the question of contact-induced change in English where it is a minority language (e.g. Quebec anglophones).
