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You've probably experienced it before: you go to the grocery store or wherever, and for some weird reason, coming back seems to take a lot less time than getting there did. Weirdly less time.

Suspiciously less time. What kind of wibbly-wobbly timey-wimey stuff is this?! Well, good news.

You probably weren't abducted by aliens or anything like that. And unless you got stuck in traffic or something on the way out, your route back wasn't actually shorter. You're just experiencing the return trip effect because your brain isn't all that accurate at estimating how long things take.

This feeling that the way back is shorter is so universal that psychologists have been trying to understand why it happens for decades. Back in the 1950s, researchers proposed that it was due to familiarity, which would kind of make sense. They figured that on the way out, you're actively paying attention to all sorts of new sights, so you really feel every second as it passes.

But on the way back, while you might note a few landmarks, you just aren't noticing things the same way because you've seen it all before. And because you're paying less attention, your ability to estimate time gets a little, well, warped. There's evidence that things like attention to the passage of time, the number of events we experience during a period of time, and stuff like boredom and impatience can mess up how you perceive time.

And familiarity could potentially affect any of those. But… there's actually not much support for the idea that familiarity is to blame. For example, one study found that as long as participants watching a video had the sense that they were moving, just being told that the way back was the way back was enough to make it feel shorter.

Which is bonkers. And more studies have found that you don't actually perceive the time wrong in the moment. When participants in a 2015 study were asked to tell the researchers every time they thought three minutes had passed, they did equally well when watching videos of an outbound trip, a return trip, and an alternate route of the same length.

But when reflecting on the experience afterwards, all of a sudden, they thought the return trip video was shorter than the other two. So, you know, hindsight not so 20/20. This all suggests that the return trip effect has something to do with the stories we tell ourselves after the fact, not how we perceive time.

Weird and cool as that is, though, it doesn't tell us why we make the error. The most recent idea, which seems to be gaining traction among psychologists, is that it happens because of a violation of expectations. In general, we're pretty bad at estimating how long things will take.

Anyone who has ever waited until the last minute to write a paper or packed desperately 45 minutes before their flight takes off knows this very well. So, like most things in our lives, we think the outbound trip will take less time than it actually does. And that makes it feel paiiiiiiiinfullllllyyyyyy looooooong.

Then, on the return trip, we adjust our expectations: it's gonna take forever and we just gotta deal. But the sheer misery of the outbound trip means that we overestimate the return trip. We expect it to be extra paiiiiiiiinfullllllyyyyyy looooooong, and then we end up being pleasantly surprised by how short it is.

But, of course, that's just a hypothesis — so a 2011 study published in Psychonomic. Bulletin & Review tested it and the familiarity hypothesis head-to-head. They had 93 college freshmen bike to a forest for some get-to-know-you bonding games at the beginning of the school year.

The students biked out one way and then came back either the same way or a new and different way that took the same amount of time. The return trip effect showed up regardless of which way they went back, so familiarity didn't make the rides feel shorter. But the effect was more extreme when the student thought the outbound trip took longer than they'd expected it to.

In fact, the more off their expectations were at first, the worse they were at judging how long it took to get back. ... Which is exactly what you'd expect if it was expectations, not familiarity, causing the return effect. And that fits nicely with the other studies.

Ultimately, it's more about how we think about and frame the return trip in our minds than what's happening in the moment that matters. And that also potentially answers another timeless question: why your daily commute always feels so long. You know every inch of your route to work all too well, so you're super good at predicting how long it will take — and that means you're rarely pleasantly surprised.

Thanks for watching this episode of SciShow Psych! If you like this episode, you might also like our episode on whether doorways really make you forget things. [ ♪ OUTRO ].