This is a handy study for a lot of students. Does it hurt to watch those online lesson videos at a higher speed?

Therefor Dillon Murphy and colleagues did 3 experiments:

Specifically, in Experiment 1, participants watched lecture videos at either normal (1x) speed or increased speeds (1.5x, 2x, or 2.5x) and were tested on the video content both immediately and after a delay (1 week). To further investigate the most efficient methods for watching lecture videos, in Experiment 2, we examined whether watching a video twice at 2x speed results in better learning outcomes than watching a single time at 1x speed. In Experiment 3, we tested how different study schedules (watching first at normal speed and again at 2x speed or first at 2x speed and then again at normal speed) affect comprehension.

Let’s check the results:

…in Experiment 1, we tested learners’ immediate and delayed (1 week) comprehension after watching videos at either 1x, 1.5x, 2x, or 2.5x speed. As predicted by participants, results revealed that video speed had little effect on both immediate and delayed comprehension such that participants only showed comprehension deficits when watching at 2.5x speed compared with 1x speed. Such learning impairments are consistent with the Cognitive Load Theory (see Sweller, 1988, 1989) and the Cognitive Theory of Multimedia Learning (Mayer, 2002) such that when the material is presented at faster than 2x speed, the rate of presentation results in a cognitive load that exceeds learners’ limited cognitive resources. However, because there appear to be minimal costs incurred by increasing video playback speed up to 2x speed, it is possible that faster presentation speeds do not overly tax working memory as long as the speeds do not exceed 2x speed.

Ok, that’s good news, but it can even help if you use it for spaced practice:

…in Experiment 2, we investigated whether watching a video twice at 2x speed rather than a single time at normal speed resulted in better learning outcomes. In Experiment 2a, despite participants watching once at 1x speed predicting better performance than participants watching twice at 2x speed (in immediate succession), the two groups performed similarly on the comprehension test.

However, in Experiment 2b, participants either watched the videos initially at 1x speed or 2x speed but following a 1-week delay, participants who watched at 1x speed took the comprehension test while participants who initially watched at 2x speed rewatched the videos before taking the comprehension test. After the initial viewing session, both groups predicted similar performance but following the 1-week delay and some participants rewatching the videos at 2x speed, participants watching the videos twice at 2x speed expected to perform better than participants watching once at 1x speed. Mirroring the latter predictions, when the study sessions were spaced in time (i.e., when there was a 1-week delay between encoding sessions) and the second 2x viewing occurred immediately before the test, watching the videos twice at 2x speed led to better performance. Thus, students may be able to study more efficiently and enhance learning outcomes by watching their asynchronous lectures initially at 2x speed and again at 2x speed immediately before the test rather than watching a single time at 1x speed with a long delay before the exam.

And what does the third experiment teach us?

Lastly, to investigate whether learners can enhance the benefits of repetition, participants in Experiment 3 watched each video twice: either initially at normal speed and then again at 2x speed or initially at 2x speed and then again at normal speed. However, both predictions and performance did not differ as a function of study schedule whether participants watched the videos in immediate succession or with a 1-week delay between viewings. Thus, Experiment 3 indicates that watching lecture videos multiple times at different speeds may not be an effective study strategy to enhance comprehension.

So the good news is: you can watch those videos at double speed, not faster, and watch those videos a couple of times as a means of spaced practice.

Abstract of the study:

We presented participants with lecture videos at different speeds and tested immediate and delayed (1 week) comprehension. Results revealed minimal costs incurred by increasing video speed from 1x to 1.5x, or 2x speed, but performance declined beyond 2x speed. We also compared learning outcomes after watching videos once at 1x or twice at 2x speed. There was not an advantage to watching twice at 2x speed but if participants watched the video again at 2x speed immediately before the test, compared with watching once at 1x a week before the test, comprehension improved. Thus, increasing the speed of videos (up to 2x) may be an efficient strategy, especially if students use the time saved for additional studying or rewatching the videos, but learners should do this additional studying shortly before an exam. However, these trends may differ for videos with different speech rates, complexity or difficulty, and audiovisual overlap.