Accelerating the playback speed to one and a half times or double has little effect on the comprehension of online lectures, as has been shown in research. Scientists have explored how the playback speed of learning videos affects the learning effect in different experiments. Participants who played the video twice as fast performed similarly on a subsequent knowledge test as those who watched the video at normal speed. Comprehension difficulties only set in at two and a half times the normal speed. 85 percent of all participants in the study stated that they usually watched video lectures at increased speed.
Follow-up experiments tested the influence of watching an educational video twice at double speed. The results of the knowledge test hardly changed in the study in comparison to watching the lecture once at normal speed, if the lecture was watched twice at double speed and the test was performed directly afterwards in each case. However, when there was a one-week delay in testing what participants had learned, those who watched the video a second time at double speed just before the test performed better than subjects who had watched the video once at normal speed a week earlier.
It is concluded that students could strategically divide their study time by watching lectures twice at up to double speed, with the second time being just before an exam. It should be noted, however, that the results of the study are limited by the fact that more complex topics might be less easily learned at increased speed or, for example, visual elements might not be discernible due to the acceleration.