Chapter 1 provides an overview of screen time concerns reported in the media and research, with consideration of relevant learning and interaction theories which indicate that face-to-face social interaction, talk and play are essential for the linguistic and cognitive development of children. This chapter also revisits the fundamental multimodality of face-to-face interaction. The shift from face-to-face to online multimodal interaction therefore requires users to make complex linguistic and interactional adaptations to be able to achieve understanding and affiliation with interlocutors in online contexts, as occurred with the advent of the telephone. This is especially true of the most common form of online interaction, text chat, which is a unique hybrid form of social written interaction, with its own specific affordances and constraints for children’s social and linguistic development. This chapter presents key interactional differences between face-to-face and written online interaction, based on conversational resources available (or unavailable) to users in either setting, including videogame settings. This discussion provides a necessary basis for investigation of children’s written interaction in subsequent chapters.

The effect of English Medium Instruction (EMI) on language learning has been a classic and extensively discussed topic in EMI research, with various methods used to address it. One reliable method is corpus-based analysis, which provides quantitative evidence about the development of learners’ linguistic competence within an EMI context. This paper chapter aims to introduce the application of corpus-based analysis in EMI research through three tasks. Firstly, it summarizes relevant literature exploring the effects of EMI on English learning. Secondly, it elaborates on how to use corpus-based analysis to conduct relevant studies, including corpus construction, linguistic analysis instruments, and statistical analyses. Lastly, it presents an example study that demonstrates the value of corpus-based analysis in EMI research. The study examines learners’ longitudinal development of phraseological competences within an EMI course and explores the effect of textbook input on language learning. The data for the study consisted of learners’ written productions at three data collection times in the course. Learners’ phraseological competence was measured by eight measures targeting bi-grams’ and tri-grams’ complexity. The study found noticeable growth in learners’ phraseological competence with EMI education’s progression and similarities between high-frequency bi-grams and tri-grams in textbook input and learners’ written productions, proving the effect of the input on language learning.