Many students are trying to save time by watching their lectures at higher speeds, but how effective is it? Is it really as revolutionary as it might seem?

Some studies show decreased learning at higher speeds. For example a study by Song and associates had 54 medical students watch videos about sonography at 1x and 1.5x speed. They found evidence of poorer performance on a subsequent multiple-choice quiz for those students that watched the videos at 1.5x [1]. Similarly, an experiment by Chen and associates found evidence of a negative effect of increasing lecture video speed on learning. Those who watched a video at 2x speed performed worse on a subsequent test than those who watched the video at 1x [2].

In contrast, other experiments have found that speed can be increased up to 2x without a reduction in learning. Murphy and associates found little difference in comprehension to 1x viewing when students watched at 1.5x or 2x. Comprehension was only impaired at 2.5x, suggesting that students should limit their viewing to 2x at the most [3]. However, the viewing materials were "real estate appraisals" and "the history of the Roman Empire", it might be difficult to generalise the conclusions to more complex materials. In another experiment by the same team, they found that watching a video initially at 2x then again at 2x speed after a one-week delay was superior to simply watching it once at 1x speed. The key is likely the delay between viewing sessions as when videos were watched twice at 2x speed in quick succession there was no benefit over watching it once at 1x speed [3].

Similar results were found by other research teams. Nagahama and associates failed to find any differences in comprehension between those who watched videos at one of three speeds 1x, 1.5x, and 2x [4]. As did a study by Tran and associates, which noted no negative effect on memory up to 2x speed. Beyond 2x speed memory began to be impaired [5]. It’s worth noting that participants in the Tran study were undergraduate psychology students, and the videos they watched were about psychology. If the material was unfamiliar and complex, then evidence of memory impairment might begin at lower viewing speeds.

For more mature students, it might pay to hold off watching videos at faster speeds. A series of experiments by Murphy and associates were consistent with earlier studies in that younger adults were able to watch videos at 2x speed without performance deficits. However, there was some evidence of impairment for older adults when videos were watched at 2x speed, suggesting that faster playback speeds may have overwhelmed older adults’ cognitive resources [6]. It’s worth noting that the older adults in the experiments were all aged over 60 and the average age was in the 70s, which is probably outside the age range of most mature university students. Nevertheless, middle-aged students might want to exercise restraint and watch lectures at speeds of 1.5x or lower. They might even consider playing lectures at slower than normal speeds such as 0.75x if it assists understanding. Overall though, older adults should not feel discouraged by Murphy’s results, as in many of the experimental conditions the older adults performed similarly to the younger adults on memory tests.

In conclusion, the evidence is mixed, and the exact speed at which a video can be watched without reducing comprehension likely depends on a number of factors such as difficulty of material, prior knowledge, and other personal characteristics. Start with lower speeds such as 1.25x and 1.5x. Only tackle higher speeds such as 1.75x and 2x if you feel comfortable. Since there is substantial evidence of impaired learning beyond 2x, speeds over 2x are not recommended.

In addition to the impact of speed on learning, there is also the issue of how speed affects enjoyment of watching the lectures. A number of studies point to increased playback speed negatively impacting the experience of the lecture. This could be because higher playback speeds require more effort.

A study of users of Stanford University’s now retired Lagunita MOOC (Massively Open Online Course) platform found that when students could select which speed to watch a video they typically chose a speed between 1.25x and 1.5x [7]. This is consistent with studies by Nagahama and associates which found that when given the choice between 1.5x and 2x, students preferred 1.5x as 2x was perceived as difficult to watch [4, 8]. A 2024 article by Tran and associates also found that higher playback speeds were perceived negatively and that this negative perception occurred prior to any impact on memory or attention [5].

If watching videos is a negative learning experience, then learners are likely to feel less motivated and will instead procrastinate leading to a decrease in productivity. For this reason it is recommended that students are cautious about increasing viewing speeds above 1.5x.

Some studies have suggested that higher speeds reduce mind wandering when viewing. This could be one mechanism by which the increased cognitive costs of watching high speed video are offset to maintain comprehension [6]. One experiment by Murphy found evidence of reduced mind wandering at higher speed, whereas another failed to show this. Furthermore, the study by Tran also found no effect of increasing playback speed on reducing mind wandering [5]. Thus counting on higher video speeds to reduce mind wandering may not be a good strategy. It is worth noting that there is a general trend of mind wandering increasing as a lecture progresses, perhaps indicating the difficulty of maintaining attention as the amount of information processed builds up [5].

For those students who suffer from mind-wandering, trying to solve this simply by speeding up the video may not work. Instead, they may need to consider other strategies such as using effective note-taking techniques as well as watching the lectures in shorter chunks such as 10 minutes each. Speeding up the video slightly may allow short breaks every 10 minutes while still completing the video within the original duration (of say 50 minutes).

Taking notes during lectures is thought to help reduce mind-wandering and improve focus. A concern is how note-taking effectiveness might be impacted by higher speed viewing. This relationship was explored in a series of experiments by Chen and associates.

In the first experiment, students watched videos about the Paleozoic era and principles of microeconomics and were assigned to a variety of experimental conditions regarding video speed and note-taking on a laptop. Students were unable to pause the video and had to watch it continuously to completion. Those who watched the video at 2x speed performed worse than those who watched at 1x speed, but taking notes improved test scores.

A second experiment involved long-hand note-taking instead of a laptop. Overall, Chen concluded that increasing speed had a negative effect on learning, but that taking notes helped improve test scores [2]. There was some evidence that long-hand note-taking was superior as viewers took down less verbatim content and instead summarised and synthesised knowledge which led to improved learning.

Being able to watch videos at home not only saves time and money wasted on commuting, but can save additional time if the lecture can be watched at 1.5x or even 2x speed. For students that want to try higher speeds, it’s recommended they try 1.25x then proceed to 1.5x. If they find they can still understand the video and take useful notes, they may want to try a further speed increase to 1.75x or 2x. But, they should proceed cautiously as evidence associates these higher speeds with decreased learning. In addition, 2x might be okay for some simpler material, but less feasible for more complex topics.

Students often find watching at higher speeds to be a less enjoyable experience which needs to be weighed up against any efficiency gains. This negative lecture experience can start occurring even before memory performance is impaired which is one more argument in favour of limiting speed boosts to around 1.5x.

Studies to date have only incorporated a small range of scenarios, if students have several hours of lectures to watch each day the results may be different as even moderate speed increases could result in fatigue and cognitive overload. Be aware also that we aren’t necessarily good judges of how well we are learning.

The research on video speed is mixed, suggesting that there is no definitive answer, but rather that the maximum speed depends on a number of interacting factors, including:

Overall then it is thought that most people have sufficient cognitive reserves for moderate increases in playback speed, but beyond a certain level cognitive capacity becomes overloaded. Easier material is compatible with higher playback speeds without overwhelming our cognitive resources. However, the corollary to this is that the more complex material, the lower the playback speed that is needed in order to understand the content. Novel and complex material can likely only be optimally processed at lower speeds such as 1x or 1.25x. Speeds such as 1.5x or 2x are probably fine for simpler material or when reviewing material that is already familiar.

[1] K. Song, A. Chakraborty, M. Dawson, A. Dugan, B. Adkins, and C. Doty, “Does the podcast video playback speed affect comprehension for novel curriculum delivery? A randomized trial,” Western Journal of Emergency Medicine, vol. 19, no. 1, p. 101, 2017.

[2] A. Chen, D. H. Murphy, J. A. Brabec, R. A. Bjork, and E. L. Bjork, “The effects of lecture speed and note-taking on memory for educational material,” Applied Cognitive Psychology, vol. 38, no. 1, p. e4166, 2024.

[3] D. H. Murphy, K. M. Hoover, K. Agadzhanyan, J. C. Kuehn, and A. D. Castel, “Learning in double time: The effect of lecture video speed on immediate and delayed comprehension,” Applied Cognitive Psychology, vol. 36, no. 1, pp. 69–82, 2022.

[4] T. Nagahama and Y. Morita, “Analysis of learning effectiveness with high-speed visual content,” Educational technology research, vol. 40, no. 1, pp. 85–95, 2018.

[5] S. Tran, L. J. Bianchi, and E. F. Risko, “Examining increasing playback speed in recorded lectures on memory, attention, and experience,” The Journal of Experimental Education, pp. 1–19, 2024.

[6] D. H. Murphy, K. M. Hoover, and A. D. Castel, “The effect of video playback speed on learning and mind-wandering in younger and older adults,” Memory, vol. 31, no. 6, pp. 802–817, 2023.

[7] D. Lang, G. Chen, K. Mirzaei, and A. Paepcke, “Is faster better? A study of video playback speed,” in Proceedings of the tenth international conference on learning analytics & knowledge, 2020, pp. 260–269.

[8] T. Nagahama and Y. Morita, “Effect analysis of playback speed for lecture video including instructor images,” International Journal for Educational Media and Technology, vol. 11, no. 1, 2017.