Quantity and quality of input affect language development, but input features also depend on the context of language emission. Previous research has described mother-child interactions and their impact on language development according to activity types like mealtimes, book reading, and free play. Nevertheless, few studies have sought to quantify activity types in naturalistic datasets including less-studied languages and cultures. Our research questions are the following: we ask whether regularities emerge in the distribution of activity types across languages and recordings, and whether activities have an impact on mothers' linguistic productions. We analyse input for two children per language, at three developmental levels. We distinguish three activity types: solitary, social and maintenance activities, and measure mothers' linguistic productions within each type. Video-recorded activities differ across families and developmental levels. Linguistic features of child-directed speech (CDS) also vary across activities – notably for measures of diversity and complexity – which points to complex interactions between activity and language.

Despite its rather shallow origin, Arabic forms the largest group of extant Semitic languages and one of the most geographically widespread languages of the world. The current distribution of its linguistic variants is the product of a phylogeography of the populations that spoke them, and Arabic dialects have captured in their words and structures traces of their speakers demic history. In this paper, we show how a phylolinguistic approach can identify such traces and make sense of them in terms of population contacts and migration, and discuss how its findings fit with the cumulative knowledge of the history and genetics of arabic-speaking populations.