We argue that language learning occurs in triadic interactions, where caregivers and children engage not only with each other but also with objects, actions and non-verbal cues that shape language acquisition. We illustrate this using two studies on real-time interactions in spoken and signed language. The first examines shared book reading, showing how caregivers use speech, gestures and gaze coordination to establish joint attention, facilitating word-object associations. The second study explores joint attention in spoken and signed interactions, demonstrating that signing dyads rely on a wider range of multimodal behaviours – such as touch, vibrations and peripheral gaze – compared to speaking dyads. Our data highlight how different language modalities shape attentional strategies. We advocate for research that fully incorporates the dynamic interplay between language, attention and environment.