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The magic number for lesson engagement

By Robert Barakat on 29 January 2016StrategyNSWstaffroom

The average length of a lesson in high school is about 50 minutes, but have you ever wondered how long your students are really paying attention for? We investigated the data from over one million video lesson views, studying the the link between lesson length and student engagement rates. The results? Less than you'd think.

It turns out that about six minutes is the magic number.

To confirm that we weren't looking at some kind of unique anomaly specific to our data set, we did some further digging and found that a study undertaken by a number of professors at the University of Rochester and MIT. They looked into the effects of learning via video and confirmed an initially surprising fact:

The most significant indicator of engagement is video length, not our kaleidoscopic colour palette, or our digital tablet drawing, or even our creative analogies, but the length of time in which we do all of this proved most imperative.

Our results showed pretty clearly that the nine-minute mark of a lesson sees brains all but shut off, eyes glaze, and the quality of learning falls staggeringly. Alternatively, a six minute video is optimum for ensuring students are not only paying attention, but absorbing knowledge as it's being presented. After six minutes you're losing your audience pretty quick!

Boxplots - engagement vs video length

Figure 1: Boxplots of engagement times in minutes (top) and normalised to each video’s length (bottom).

In each box, the middle red bar is the median; the top and bottom blue bars are 25th and 75th percentiles, respectively. The median engagement time is at most 6 minutes.

Although the data doesn't provide reasons, we'd speculate that it might be due to the the following:

Students’ attention spans

It's easy to blame the information age and the death of long form media for relegating the youth's attention spans to little beyond the length of a commercial, but its the world we live in. You could argue that we're adapting to our new world, or that our world is just catching up with how we naturally work best. Regardless, the cat's out of the bag on this one.

Information saturation

In six minutes you can actually cover a surprising amount of ground. It's no wonder that a student might start to get a little bit distracted if they're struggling to keep up with all the new information dropped on their plate. Taking a break after six minutes to summarise and consolidate helps information sink in, rather than flying over heads.

So, how do we take advantage of it?

Interestingly, for us here at Atomi, fitting content into shorter videos actually means more work. It means that every lesson needs to be edited and refined, with the most integral concepts identified and targeted in a rigorous pre-production phase. This means we’re only delivering the content that is most critical to understanding and communicating a topic. No time for waffling.

In the classroom, it simply means chunking lessons and activities into smaller blocks, which we call sprints. In a 50 minute lesson you can squeeze in roughly six sprints of six minutes with two minute breaks in between. You can adjust that math to fit your school's lesson length, but just make sure your sprints don't exceed the six minute mark.

In a traditional (non-flipped classroom) we'd recommend alternating sprints of content and problem solving. For a flipped classroom we've seen great results from alternating sprints between huddles (teacher lead examples, group discussions and student lead presentations) and individual problem solving.

Six minutes are all you need to boost your classroom participation and enhance your students’ understanding and enjoyment, so use them wisely!


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