The present pre-registration aims to investigate the role of language as a dimension of social categorization. Our critical aim is to investigate whether language can be used as a dimension of social categorization even when the languages coexist within the same sociolinguistic group, as is the case in bilingual communities where two languages are used in daily social interactions. We will use the memory confusion paradigm (also known as the Who said what? task). In the first part of the task, i.e. encoding, participants will be presented with a face (i.e. speaker) and will listen to an auditory sentence. Two languages will be used, with half of the faces always associated with one language and the other half with the other language. In the second phase, i.e. recognition, all the faces will be presented on the screen and participants will decide which face uttered which sentence in the encoding phase. Based on previous literature, we expect that participants will be more likely to confuse faces from within the same language category than from the other language category. Participants will be bilingual individuals of two bilingual communities, the Basque Country (Spain) and Veneto (Italy). The two languages of these communities will be used, Spanish and Basque (Study 1), and Italian and Venetian dialect (Study 2). Furthermore, we will explore whether the amount of daily exposure to the two languages modulates the effect of language as a social categorization cue. This research will allow us to test whether bilingual people use language to categorize individuals belonging to the same sociolinguistic community based on the language these individuals are speaking. Our findings may have relevant political and social implications for linguistic policies in bilingual communities.