Welcome to Bad Ideas, a column in which we examine the practical limits of technology by considering the things you could do, and then investigating exactly why you shouldn’t. Because you can still learn from mistakes you’ll never make.
Most of us are familiar with binge watching and speed reading, but there’s a relatively new mode of conspicuous consumption that’s emerged in recent years: podfasting. First profiled in 2017, podfasters love listening to podcasts so much that they’re speeding them up — 1.25x, 1.5x, and even 2x speed — in order to fit more into their day.
Podfasters often draw the ire of podcast creators, who object to listeners steamrolling over their carefully edited audio. Meanwhile, podfasters argue they’ve identified a “flaw” with the podcast as an information delivery medium: People speak out loud at an average of 150 words per minute, while our brains internally yammer along at 400 words per minute. If your goal is to upload the information contained in a single podcast episode into your brain then, it would seem, human speech is a bottleneck. Could you train yourself to listen to a podcast at 2.5x or even 3x?
As soon as the podfasting craze emerged, listeners pushed themselves to the limit — and apparently found one. Uri Hasson, director of Princeton’s Hasson Lab, a neuroscience lab that studies the brain’s response to natural life events, found that word recognition drops about 40% when audio is played back twice as fast. Raymond Pastore, an instructional technology professor whose research focuses on speeding up our aural comprehension, told The Ringer that 2x was the average human limit.
But the human body is capable of incredible feats. The sub-four-minute-mile was impossible, until Roger Bannister broke it — and now even high schoolers are running sub-fours. With the right training, can we hack our brains to break 2x? Could I be the Roger Bannister of podfasting?
I reached out to Hasson, and posed a simple question: Just how much can we train our brains to listen faster? “The brain is very flexible,” he says. “Practice will make you better.”
Our brains are remarkably good at speech recognition. Everyone has a unique way of speaking — accent, tone, and cadence all differ from person to person, and yet our brain can understand it all more-or-less perfectly at normal speed. Raise the speed, or compression as Hasson calls it, and your brain starts to struggle with the unfamiliar speech pattern.
While we can’t train our brains to understand everyone at high speeds, Hasson explains that we can sharpen our brain’s ability to comprehend specific voices. Listen to someone enough and you’ll develop a familiarity with their speech patterns, thus enabling you to raise the playback speed without a drop in word comprehension.
I started my brain training with a show I’ve already sunk dozens of hours into, a role-playing podcast called Friends at the Table. Bumping up the speed to 1.25x, I’m embarrassed to admit, actually made the podcast a slightly more enjoyable listen. Segments of exposition felt snappier, sequences where the players are trying to assess their options felt less drawn out, and best of all, an hour-long episode only took 48 minutes to listen to all the way through.
This isn’t surprising. Hasson explains that audio at 1.25x speed actually hits a sort of sweet spot for humans: fast enough to keep things moving without overly taxing our brains.
At 2x, the experience of listening to audio began to change: Though I could understand the words, they seemed to have less emotional resonance.
Bumping the speed up to 1.5x was initially jarring. People were talking so quickly that I had to stop what I was doing and focus on the audio to keep it from falling into background chatter. After about 20 minutes of this intentional listening, however, it felt like my brain had adjusted. What at first felt rushed and slightly wrong, now felt natural.
Once I found that I could go back to doing the things I normally do when I listen to podcasts — brush my teeth, do the dishes, fold the laundry — I bumped up the speed another notch to the 2x barrier. Like the previous jump in speed, the first 15 to 20 minutes required an additional level of focus to get my brain to match the cadence of the conversation. But once I was there I felt like I didn’t have to strain to understand what was being said — my brain just “learned” how to listen to this accelerated pace.
In our discussion of breaking 2x, Hasson brought up one population that handles sped-up speech much better than the rest of us: the visually impaired.
A 2018 University of Washington study attempted to quantify human listening rates by measuring the intelligibility of audio from a text-to-speech generator played at increasingly faster speeds. Researchers found that the average sighted person could comprehend around 300 words per minute, or about double the average talking speed of an American English speaker. Visually impaired subjects, however, vastly outperformed sighted subjects at speeds past 2x, demonstrating comprehension at rates even approaching 3x.
The researchers hypothesized that this difference between sighted and visually impaired listening rates was attributed to one group being more familiar with synthesized text-to-speech voices.
At 2x, the experience of listening to audio began to change: Though I could understand the words, they seemed to have less emotional resonance. At these high speeds, my brain seemed to shift away from assessing people’s feelings towards baseline comprehension. At the end of each sentence, I’d feel a little twinge of joy, not because of anything happening in the podcast, but just because I had understood the words.
Hasson points out that single word comprehension is really only one dimension of comprehension. Our brains do not work like computers. We can recognize words very quickly, but to integrate them into a sentence, a sentence into a paragraph, and a paragraph into a larger narrative takes time.
Feeling competent in my base-level comprehension at 2x, I crossed the threshold into 3x. It took every ounce of concentration to just register what was being said. After 20 minutes, my brain couldn’t settle into the rhythm of the conversation. I sat there for an hour, with my eyes closed, hoping that my brain would eventually “click” like it did before, but it refused.
At previous speeds, the audio would initially sound like it was on fast-forward, because it was, but not so fast that it would sound humanly impossible. It was like listening to an anxious seventh-grader give a presentation, coherent, but rushed. At 3x speed, the audio entered an aural uncanny-valley, too fast to be considered human, but slow enough at points that you could make out a phrase here, a sentence there. It was distracting in ways that the slightly-less accelerated rates were not.
Acclimating to this speed wouldn’t take hours, or even days, but likely weeks or even months before I could even follow along. And even then, how much would I actually remember? Even at 2x speed it was difficult grasping narratives.
You can train your brain to better recognize words played at increasingly faster speeds, but our cognitive ability to connect one sentence to the one before, and place it in a larger context that gives us meaning and emotion, has a limit. In other words, our ability to comprehend increasingly fast rates of speed might be boundless, but our ability to think critically about it, Hasson believes, has a hard limit.
“If you train yourself, you can really become really fast,” he says. “But you lose something in the depth of comprehension.”
Hasson wonders if this urge to listen to podcasts faster and faster might, ultimately, miss the point of listening to a podcast.
“Are you really paying attention to all the details, and getting some deep thinking, not just, like, ‘fake thinking’” he says. “Are you really going to feel it and integrate it with your own memories?” Personally, Hasson says, “I always prefer to go slow.”