As the preceding section has shown, describing a bilingual fully, at a particular point in time, and over a life time, is particularly demanding. One approach that has been used is to ask bilinguals to fill in self-report questionnaires that aim at obtaining the kind of information we described. If used along with various verbal tasks, such as picture naming, word and sentence perception and production, etc., they allow us to have a good description of those who interest us (see de Bruin 2019, for a critical review). Three major self-report questionnaires are now available in the field for adults, while other, smaller ones, examine specific behaviors (e.g., language choice and code-switching), or are aimed at describing the bilingualism of children (these are filled in by parents or caretakers).

The three self-report questionnaires are the Language Experience and Proficiency Questionnaire (LEAP-Q) proposed by Marian, Blumenfeld, and Kaushanskaya (2007), the Language and Social Background Questionnaire (LSBQ) proposed by the York University Lifespan Cognition and Development Laboratory (Anderson et al. 2018), and the Language History Questionnaire (LHQ3) proposed by Li, Zhang, Yu, and Zhao (2020). Since they have very similar acronyms, and to facilitate reading, I will use Q-A for the LEAP-Q, Q-B for the LSBQ, and Q-C for the LHQ3. I examined each questionnaire keeping in mind the factors I discussed above, those pertaining to bilinguals at a particular point in time, and those that concern their language history, and will briefly summarize what I found. This is not meant to be a critical review but simply a way of illustrating how one goes about obtaining extensive biographical language data from bilinguals, and the diversity one can find among the tools available.