Research in educational psychology correlates interest in content with engagement and learning.
in a specific topic is based on a user's longer term involvement,
investment and/or expertise.
results from the environment or how content is presented (the headline, video, etc.)

If the largest possible audience is the goal, digital content that can addresses both individual and situational interest increases the chances that more users will engage more users even though the time of users' engagement time will vary. In other words, content is no longer produced with the expectation that users will consume all of the content.

Ronald A. Yaros, Ph.D. 

University of Maryland