How to quantify bilingual experience? Findings from a Delphi consensus survey

Abstract While most investigations of bilingualism document participants’ language background, there is an absence consensus on how to quantify bilingualism. The high number different background questionnaires used by researchers and practitioners jeopardises data comparability cross-pollination between research practice. Using the Delphi survey method, we asked 132 panellists (researchers, speech therapists, teachers) from 29 countries rate 124 statements a 5-point agreement scale. Consensus was pre-defined as 75% threshold. After two rounds, 79% reached consensus. need for common measures acknowledged 96% respondents. Agreement document: exposure use, difficulties, proficiency (when it cannot be assessed directly), education literacy, input quality, mixing practices, attitudes (towards languages mixing). We discuss implications these findings creation new tool bilingual experience.