  This work addresses challenges in developing conversational assistants that
support rich multimodal video interactions to accomplish real-world tasks
interactively. We introduce the task of automatically linking instructional
videos to task steps as "Video Instructions Linking for Complex Tasks" (VILT).
Specifically, we focus on the domain of cooking and empowering users to cook
meals interactively with a video-enabled Alexa skill. We create a reusable
benchmark with 61 queries from recipe tasks and curate a collection of 2,133
instructional "How-To" cooking videos. Studying VILT with state-of-the-art
retrieval methods, we find that dense retrieval with ANCE is the most
effective, achieving an NDCG@3 of 0.566 and P@1 of 0.644. We also conduct a
user study that measures the effect of incorporating videos in a real-world
task setting, where 10 participants perform several cooking tasks with varying
multimodal experimental conditions using a state-of-the-art Alexa TaskBot
system. The users interacting with manually linked videos said they learned
something new 64% of the time, which is a 9% increase compared to the
automatically linked videos (55%), indicating that linked video relevance is
important for task learning.
