Stylex: a corpus of educational videos for research on speaking styles and their impact on engagement and learning

In the context of learning through educational videos, the material chosen for a given topic must not only be relevant but also engaging to the consumer—ensuring better understanding and retention of content. This paper focuses on the speaking style of instructors, which is an important aspect driving student engagement. We present StyleX, a corpus of 450 1-minute video clips featuring 50 instructors, 10 topics in engineering and various accents of English. With the help of a large student population (304 in total), we study the impact of four speaking-style dimensions (liveliness, clarity, fluency and formality) on engagement and learning. Based on the in-classroom evaluations of 250 clips (> 20 simultaneous evaluators per clip), we find that liveliness and clarity are the most important dimensions (correlation with engagement and learning > 0.8), followed by fluency and formality. Familiarity with topics has a significant effect on the evaluators’ ratings, while the instructors’ accent and gender do not. StyleX represents the first large-scale effort of its kind in terms of the clip duration used and the number of topics, instructors and evaluators involved. This is also the first study, to our knowledge, on the explicit relationship between speaking style and engagement.