Always Play Podcasts And Videos At 2x Speed? There May Be Some Drawbacks To That

How do you listen to recorded information? Do you listen at the regular speed, or are you among the many who digest podcasts, audiobooks, or even recorded lectures at increased playback speeds? It might be tempting to think that the faster the playback speed you’re able to follow then the quicker you’ll be able to learn the intended content. Less time spent on a single piece of content means there’s more time for other things, right? Well, maybe not. New research suggests that our ability to memorize information may not be able to keep up with our ability to follow faster content, at least at certain speeds.

With the rise of internet technologies and the disruption to in-person learning during the COVID pandemic, more institutions are offering students the chance to view pre-recorded materials. Even those that do include in-person teaching often provide video lectures to supplement their courses. This can be convenient for students who need to catch up on missed content or for learning outside of the classroom. In this context, video lectures can offer various benefits as they can be viewed at any time and rewatched as needed.

Many video players allow students to select speeds for the content that can go from 0.75x, to 1.25x, and 2x upwards. It’s a popular function. In a recent survey of Canadian undergraduate students, 89 percent reported listening to lectures at altered speeds, 96 percent of whom opted to listen at increased speeds. But how does this impact students’ ability to perform in tests?

To investigate this, researchers recently undertook a meta-analysis using data from 24 existing studies. The studies each had their own approach to the problem, but they generally involved the same thing – participants being randomly assigned to a control group that watched a lecture played at its original speed (1x), or to other groups that viewed the same recording at increased speeds (between 1.25x and 2.5x).

After watching the videos, the participants were asked to complete an identical test related to the recorded content. These tests varied in their format. Some used multiple choice questions, recall format, or a combination of the two.

The results indicated that speed is a factor when it comes to student test performance. The faster the playback option, the more significant its impact. At speeds of up to 1.5x, the impact was low, but became moderate to large for speeds above 2x.

“Overall,” the researchers expressed in their paper, “as playback speed increased the cost to content test performance increased.”

“That said, the cost to test performance at moderate and more popular levels of speeding (e.g., 1.25x, 1.5x) were small and non-significant unless combined together.”

Despite this, the team did not find any evidence that this effect was influenced by the length of the lecture or the test type. However, they did find that age appeared to moderate the effects, which became more apparent the older the age of the sample. It is possible this effect represents a weakening of memory capacity in older people, especially those between 61 and 94 years of age. Alternatively, this could reflect familiarity with the technology, especially as video lectures and the playback feature are relatively new.

“It is important to note that this moderator analysis was exploratory. It was made possible by natural variation in experimental methodologies across the studies, rather than these factors being the topic of experimental evaluation in and of themselves.”

So what causes this disparity between 1.5x speeds and the costs of faster recordings? One explanation may be related to processing capacity. Lectures delivered at regular speed leave room for learners to process the information, but faster speeds may strain their capacity. 

Future research, the team say, could focus on the potential for speed listening to increase engagement and the limits of people’s capacity to deal with it. Another area could focus on learners’ ability to control the speeds they’re listening to, rather than being randomly assigned to them.

“[I]f part of the goal is understanding the impact of learners increasing playback speed, then it is important to acknowledge that learners “in-the-wild” have control over the speed as well as the ability to pause, rewind, and rewatch video lectures. If individuals can successfully monitor their learning and control playback speed accordingly, then this would mitigate costs that might appear in studies where that control is unavailable.”

The study is published in Educational Psychology Review.