What are your plans for this weekend?

Where do you see yourself in five years?

Answering these questions requires looking into the future.

But when you make these predictions, what you're actually doing is accessing your memories.

Being able to accurately predict the future gives humans an evolutionary advantage.

I'm not talking about a fortune cookie or a horoscope that says your true love will find you next Tuesday.

I'm talking about the practical ability to anticipate when crops will be ready to harvest or to prepare for a meeting with your boss.

Planning beyond the present moment and even years into the future is indispensable to human life in society.

But how do we do it?

Researchers believe that we rearrange our memories of the past to put together a vision of what the future might look like.

They've discovered that memories and predictions take place in the same regions of the brain and appear to use the same underlying processes.

Scientists first learned about this connection by observing amnesia patients.

Not only were these patients unable to access their memories, but they also didn't have any idea of what they might do in the future.

More recently fMRI studies have allowed researchers to see into the brains of healthy people while they remembered the past and predicted the future.

The psychologist Carl Spooner observed that the activity in the brain during both tasks was almost completely overlapping.

Researchers have also found that as people age and start to develop memory loss, their ability to imagine the future declines as well.

This ability to envision moments in both the past and the future is known as mental time travel.

Mental time travel is different from just remembering facts.

It's about reliving scenes in your mind.

If you think about the last time you went to the beach your brain reconstructs the setting.

You feel the sunshine on your skin and the sand between your toes and you can smell the salt on the breeze.

In a similar way, when you imagine an event in your future, you're essentially pre-living it.

You construct a similar scene using details from your memory.

So the next time you plan a beach trip, you can imagine the feel of the sun in the sand before you've even packed your sunscreen.

Likewise, if you're imagining your future wedding, you'll probably cherry-pick elements from weddings you've been to as well as weddings you've seen on TV and movies or in magazines.

But the ability to predict the future using your memories does have one big disadvantage.

People often expect the future to be too much like the present.

Studies back up the conventional wisdom that if you go to the grocery store when you're hungry, you'll buy too much food, not realizing you won't always be this hungry.

Similarly, if you try to predict how you'll feel in the future about something, you're likely to be blinded by your current emotions.

For a vivid example of how future predictions are affected by the present, just watch an old sci-fi movie.

Take Back to the Future 2, which was made in 1989 and set in 2015.

It successfully predicted things like videoconferencing, drones, and facial recognition, but it assumed people would be still be using fax machines and pay phones.

Two technologies integral to life in the '80s which the filmmakers seemingly couldn't imagine a future without.

The future is always going to be full of surprises we can't predict.

But one thing's for sure, without our memories, we'd be totally in the dark.

This is You Are Here, a series about the science behind everyday life.

Tell us what topics you'd like us to discuss in the comments.

I'm Julie Beck, thanks for watching.