Almost anyone will tell you that long road trips feel eternal. This effect, researches say, happens because humans make pretty terrible timekeepers. We have no master clock in our brains that ticks the passage of each second. Rather, neurons all over our noggins track time, with different regions triggered by distinct stimuli—like the need to wait for a reward or clap to a beat. And these neutrons are easily swayed by other mental processes, like attention.

Paying attention to time activates the brain’s supplementary motor area (SMA), says Jennifer Coull, an experimental psychologist at Aix-Marseille University in France. The more we note time’s passage, the more active the SMA becomes, she says, and neuroscientists think the brain misinterprets more SMA activity as more time passed.

In studies where people were told in advance that they’d be asked how long a task took, participants focused on time passing and overestimated the activity’s duration. Those unaware they’d be asked these queries attended only to the task, and underestimated the time to complete it.

The same effect is true in a car. Frustratingly, the best way to pass time is to ignore it, which is much easier said than done.

This article was originally published in the Spring 2019 Transportation issue of Popular Science.