We have all felt it. The return trip from some place seems to be quicker that the outward trip, especially if you were going to a new place. I used to think that this was due to the fact that on the return trip we were now familiar with the route, which meant that we did not have to pay close attention to where we were going and that this somehow translated into the journey seeming to be shorter

But a new study both confirms that the effect is real and finds that there is more to the explanation than what I had thought.

Three studies confirm the existence of the return trip effect: The return trip often seems shorter than the initial trip, even though the distance traveled and the actual time spent traveling are identical. A pretest shows that people indeed experience a return trip effect regularly, and the effect was found on a bus trip (Study 1), a bicycle trip (Study 2), and when participants watched a video of someone else traveling (Study 3).

The authors listed the common explanations for the phenomenon (citations omitted), the main one being my own preconception that familiarity was the cause.

If a return trip effect exists, one possible cause might be an increase in familiarity and predictability. Previous research has shown that novel tasks are often remembered as taking longer than they actually do, while familiar tasks are remembered as taking less time. Similarly, tasks that are unpredictable are remembered as taking longer than similar coherent or predictable tasks. The unpredictability of the initial leg of the trip may make it so that it is remembered as being overly long. Conversely, the return trip is remembered as being short because it is now more familiar and predictable.

The authors found evidence against that idea, finding that “The return trip effect also existed when another, equidistant route was taken on the return trip, showing that it is not familiarity with the route that causes this effect.”

They thought another possibility existed that could explain the effect.

Alternatively, the return trip effect could be due to a violation of expectations. People often predict that tasks will take less time than they actually do. In general, people are fairly inaccurate when estimating how long things either have taken in the past or will take in the future. It may be that people have an expectation for a trip that is overly short, leading to a violation of this expectation when they take the trip. Hence, the initial trip takes longer than expected. For the return trip, the expectation is likely to be based on the experience of the (disappointingly long) initial trip. This leads to an upward adjustment in expectations for the return trip that is, happily, unmet. The return trip, therefore, feels shorter than the initial trip.

It is undoubtedly true that we often underestimate how long something will take to do. It is very rarely that I am surprised by something taking less time than I had allotted to it. The authors found support for this alternative explanation.

The results indicate that the return trip effect is not due to an increase in familiarity, since the return trip effect also exists when people travel a different but equally long trip back. Instead, the return trip effect is likely due to a violation of expectations. Participants felt that the initial trip took longer than they had expected. In response, they likely lengthened their expectations for the return trip. In comparison with this longer expected duration, the return trip felt short. The greater the participants’ expectations were violated on the initial trip, the more they experienced the return trip effect (Studies 1 and 2). In Study 3, where participants’ expectations for the duration of the initial trip were increased via a manipulation, the return trip effect disappeared.

It is always interesting when one’s beliefs about the causes of everyday phenomena get overturned.