It turns out how you dream depends on 2 things.

Dreams are an enigma — they are intensely personal, often make no sense, and half the time we don't even remember them. Do you ever wonder if there's an entire realm out there that we simply forget every time we wake up? Spooky.

The interpretation of dreams goes way back. In some cultures, dreams are seen as a way to communicate with the divine, in others they're seen as a guidance or warning, and some would say they show repressed desires.

Dreams can represent our greatest fears or our most private aspirations, depending on who you ask, though the way we think about and respond to dreams has changed pretty drastically over recent years.

Compared to everything else we know about the way our brains function, the actual science around our dreams is a relatively infant field. What we do know, though, is the way we dream can actually change as we age, and those of us who grew up in different times may actually dream differently.

What actually is a dream?

A dream can be defined as a succession of images, ideas, feelings and/or sensations that occur in our minds when we sleep, usually in the REM (rapid-eye movement) part of our sleep cycle. Heaps of animals dream, including mammals and birds.

Dreams are typically involuntary, and one usually lasts between five and 20 minutes — even the ones that feel years long! Humans usually dream for around two hours per night, and dreams make up about six years of our average lifespan.

Despite the leaps and bounds we've made in researching psychology and neurology, it's not clear where in the brain dreams originate (if there is even one spot), or what the actual function of dreaming is. Though, some people reckon they have an idea.

Why do we dream?

While we have quite a bit of research on how dreams affect our brain, the purpose of dreams is still pretty unclear.

Sigmund Freud was the founder of psychoanalysis, which delves into dream theory. He believed that our dreams signified repressed sexual longings and desires that we weren't able to express in a social setting. It's worth noting that he lived in the infamously sexually repressed Victorian era.

Carl Jung, a Swiss psychiatrist from the early 1900s, argued that dreams are a way for us to reflect on our waking selves and problem solve (which I personally find compelling, given the amount of times I've dreamed about issues that are stressing me out in real life).

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Allan Hobson and Robert McCarley are more modern dream researchers. In the 1970s, they posited that dreams are actually totally random electrical impulses and byproducts of our memories. This is called the activation-synthesis hypothesis.

And more recently, Professor Joseph De Koninck, from the University of Ottawa's School of Psychology, has studied dreams for more than 50 years. He told the Washington Post earlier this year that dreams are "open season for the mind".

Do we dream in black and white or colour?

Back in the day, black and white dreaming was not only common — it was considered the norm. In fact, dreaming in colour was considered an indicator that something was wrong. However, it's recently come to light that people dream in colour often, if not in most of their dreams. (I didn't even know you could dream in black and white until now!)

A 2017 study showed that participants reported colour in about 50 per cent of their dreams, and 40 per cent said they couldn't remember. Only 10 per cent of people actually reported dreaming in black and white.

However, it turns out that the colours you dream in may have something to do with your age.

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How dreams can change as you age.

Sleep patterns change as we age — we tend to sleep less as we get older, and the time we spend in REM sleep also decreases. But did you know the way we dream can also be affected by our age?

The tendency to dream in black and white could be linked to growing up watching black and white TV. A 2008 study found that people older than 55 at the time — who were more likely to have watched black and white TV growing up — reported dreaming in colour a lot less than those aged under 25.

But then again, it's also possible that we simply do not notice colour in our dreams as much as we age, rather than our actual dream-style changing.

In a 2011 study, participants took part in a longitudinal study that surveyed them at the the age of 30 and then 60. About 80 per cent of the participants reported colour in their dreams when they were 30, and only 20 per cent did at 60.

It just goes to show that with dream studies often relying on self-reporting — which isn't objective and relies on memory — it's hard to get any concrete answers!

What we dream about can change with age.

Research also shows that what we dream about can change as we age and enter different stages of our lives.

Children have more animals in their dreams than adults, likely because they have a greater salience in children's lives thanks to cartoons, books and pets, dream researcher Kelly Bulkeley told Washington Post.

He also noted that children have more nightmares than adults, which he believes is because they are aware of their smallness and vulnerability.

Bulkeley said adolescent dreams tend to be "hotter", in that they have more aggression, sex and emotional intensity. They also tend to feature friends more than family.

Young people have sex dreams more frequently. Image: Netflix.

Then, as we get older, our dreams mellow out and become less provocative. Instead, older people tend to dream more about family, strange environments, and of looking for things. They also tend to have more dreams involving death or people who have died.

Interestingly, retired social psychology professor Monique Lortie-Lussier found that women's dreams actually become more enjoyable as they age, with less conflict and aggression.

So hey, even though dreams can sometimes be a scary or uncomfortable place, it's good to know it's only up from here.