People naturally interact with the world multimodally, through both parallel and sequential use of multiple perceptual modalities. Multimodal human-computer interaction has sought for decades to endow computers with similar capabilities, in order to provide more natural, powerful, and compelling interactive experiences. With the rapid advance in non-desktop computing generated by powerful mobile devices and affordable sensors in recent years, multimodal research that leverages speech, touch,

more »

... ion, and gesture is on the rise. This paper provides a brief and personal review of some of the key aspects and issues in multimodal interaction, touching on the history, opportunities, and challenges of the area, especially in the area of multimodal integration. We review the question of early vs. late integration and find inspiration in recent evidence in biological sensory integration. Finally, we list challenges that lie ahead for research in multimodal human-computer interaction.