All in the head: Why the return trip always seems shorter

Their research found that the effect was caused not by increasing familiarity with the route but because people expected the initial trip to be faster than it was, making the trip back seem shorter.

"People seem to be too optimistic about the initial trip, so it feels longer than one expects," says Niels van de Ven, a professor of psychology at Tilburg University in the Netherlands and one of the authors of the study.

That appears to skew people's sense of what to expect on the way back "so they are happily surprised itdoesn't take as long as they expected," says Anne Wilson, a researcher who studies the psychology of time at Wilfrid Laurier University in Ontario, Canada.

People are very familiar with the effect, says Michael Roy, a psychology professor at Elizabethtown College in Elizabethtown, Pa., and one of the paper's co-authors. So much so that they are all convinced that it's because you're familiar with the route on the way back — "and yet we were able to show that's not the answer at all," he says.

The paper appears in the August edition of the journal Psychonomic Bulletin & Review.

The researchers interviewed about 350 people, including homemakers taking a bus ride to a home decorating fair and students biking to an event.

In all cases, although the trips were exactly the same length, most participants felt the return trip took less time than the initial trip.

The bike-riding students reported that the initial trip took an average of 44 minutes, while the return trip took 37. In reality, both legs took 35 minutes.

People don't experience the effect on routes they know well, such as commutes, because their "expectation is more accurate," says van de Ven.

The researchers seem to have been the first to actually study the effect, though it's been known anecdotally for decades. "It's very good research," says Richard Block, a professor of psychology at Montana State University.