Speakersʼ judgment about well-formedness is susceptible to variation in certain domainsof a language system. The usage of Turkish demonstratives bu, şu and o is one such domain. In this paper the variability of speakersʼ judgment will be used as a linguistic index characterizing a group of speakers. Turkish monolingual high school students in Istanbul, and Turkish-German bilingual peers in Berlin, participated in questionnaire surveys in which their judgments about which demonstrative was appropriate for given contexts were asked for. University students learning Turkish as a foreign language in Tokyo also participated in the survey as a control group. The results show a complete parallelism between the Istanbul and Berlin studentsʼ answers, while a considerable difference is found between the Tokyo studentsʼ answers and those of the Istanbul and Berlin students.