Parent report data on input and experience reliably predict bilingual development and this is not trivial

Carroll (Carroll) takes issue with the use of parent report to obtain quantity of language exposure measures in research on bilingual development. When discussing parent questionnaires, Carroll writes “Temporal units are crude measures of exposure and they tell us nothing about input”. While I agree that temporal units do not tell us much about the fine-grained details of the input within the temporal units, importantly, parent-report-based measures of input quantity have predicted variation in bilingual development of phonology, vocabulary and morphosyntax. These are robust and reliable findings across numerous studies, and yet, Carroll skates over them as if they did not matter, or dismisses them as trivial. Furthermore, Carroll seems to lead readers to believe that only coarse-grained, language-use temporal units have been obtained through this method; on the contrary, researchers have obtained fine-grained input quality details via parent report that also predict bilingual children's development. Finally, in some circumstances, parent report data is the only feasible method for obtaining language exposure information.