As we approach the end of the school holidays, parents across the country are saying the same thing: "If I had a pound for every time I heard 'Are we nearly there yet?', I'd be rich."

Having three young children myself, I know only too well the feeling of dread when, 30 minutes into a five-hour drive, the interrogation begins.

In our family, it starts quite politely. "Mummy, are we nearly there yet?" drifts over from the back seats.

But this approach is rapidly replaced by an aggressive cross-examination, picking apart how much longer I previously said was left of the journey versus how long I am currently saying remains.

By the end of the drive, I have promised myself that I will never take them anywhere ever again.

But why is it that journeys seem so excruciatingly long for children?

One reason is that our experience of time changes as we age, often resulting in the sensation of time passing more quickly as we get older.

This is typified by the sensation that "Christmas comes around more quickly each year".

Time is thought to pass more quickly as we age because, with increasing age, any duration of time becomes a smaller proportion of our life to date.

For example, at seven years old, a year is 14.30 percent of your entire life; at 70 years old it's only 1.43 percent of your life.

As such, a five-hour car journey may feel longer to a five-year-old than to a 50-year-old, simply because it is a greater proportion of the five-year-old's life.

But there's more to it than that. As we age, we also develop a greater understanding of distance and geography.

This knowledge provides us with markers and cues we use to understand how much of the journey is done and how much remains.

For example, on a journey from Manchester to Devon, I know that I'm roughly halfway there when we clear Birmingham, and this knowledge helps to structure the time for me. I also have access to the satnav, which provides an arrival time and warns me about upcoming delays.

The absence of this knowledge in children means that they are more reliant on asking adults how long is left to judge the progress of the trip.

No control

Children's uncertainty about how long has passed and how long remains is made worse by their lack of control over the journey itself. It's the grownups who choose which service station to stop at and which route to take. This may also contribute to the journey dragging by for children.

This is because temporal uncertainty, or the feeling of not knowing when something will happen, can slow the passage of time. As adults, many of us have significant experience of this.

Think back to the last time the train inexplicably stopped just outside the station, or when the "wait" sign flashed endlessly in baggage reclaim after a flight.

I bet neither of these delays flew by quickly – and that an update from the train driver or airport staff would have been very welcome in these moments. It's the not knowing, the lack of control, that causes these events to drag.

When there is uncertainty about time, monitoring it becomes a priority. Humans have limited cognitive capacity and can't pay attention to everything all of the time. We, therefore, prioritize what we process depending on our circumstances.

When time becomes uncertain we pay far more attention to it than normal, and this results in the sensation that time is passing much more slowly.

Time is more often uncertain for children, so without something to distract themselves, they'll fixate on the progress of any journey.

A watched pot never boils

Finally, time in the car may drag for kids simply because they're cooped up with nothing to do but stare out of the window.

That's a trial of boredom for children, while their parents in the front are likely savoring the opportunity to just sit and reflect.

Children's desire for stimulation and entertainment means that boredom often sets in quickly, and this boredom also slows the passage of time.

Like temporal uncertainty, our level of boredom affects our experience of time by altering the amount of attention that we pay to it.

When we're bored, our persistent clock-watching makes time feel like it is crawling by. Conversely, when we are happily occupied, we pay little attention to time because our attentional capacity prioritizes other things. As a result, time flies by when we have fun.

Your next journey

So what should parents do?

Those of you yet to embark on the big getaway may already be rushing to stock up on games and snacks to provide a constant stream of distractions for your kids.

However, I would urge caution. Even if you do manage to reduce the "Are we nearly there yet?" refrain, you may be increasing the risk of a new chorus: "I feel sick!"

Being covered in your child's vomit, research and experience both suggest, is highly likely to make the journey feel significantly longer for you.The Conversation

Ruth Ogden, Reader in Experimental Psychology, Liverpool John Moores University

This article is republished from The Conversation under a Creative Commons license. Read the original article.