1. Why the brain remembers dreams
Some people recall all kinds of dreams, others hardly anything. Why the big difference?
Part of the reason that some people recall more of their dreams is that they wake up more in the night, even if only for short periods.
We need to be awake to encode dreams into long-term memory, otherwise they are generally lost to the night.
2. The dream control centre
Whether you remember dreams, then, depends on whether you are a light or heavy sleeper.
A brain imaging study has found those who recall more of their dreams have higher activity in the medial prefrontal cortex (Eichenlaub et al., 2014).
In addition, those who recalled most dreams showed greater activity in the temporo-parietal junction: this area of the brain is associated with attention towards things happening in the external world.
Together these two areas are very important in dream recall.
One of the study’s authors Perrine Ruby, explained:
“This may explain why high dream recallers are more reactive to environmental stimuli, awaken more during sleep, and thus better encode dreams in memory than low dream recallers. Indeed the sleeping brain is not capable of memorizing new information; it needs to awaken to be able to do that.”
3. Daydreamers are also night-dreamers
The overlap between waking and dreaming states was at the heart of the Matrix films.
Sci-fi aside, though, the film asked: when we’re awake, are we really awake or is this just another dream?
…all heady philosophical stuff of course, but actually this has some neurobiological truth.
Neuroscientists have found that the parts of the brain responsible for daydreaming while we’re awake are also responsible for our dreaming while we sleep.
Effectively the neural substrate responsible for dreaming may be a sub-system of that responsible for our waking lives.
“…dreaming may be the quintessential cognitive simulation because it is often highly complex, often includes a vivid sensory environment, unfolds over a duration of a few minutes to a half hour, and is usually experienced as real while it is happening.” (Domhoff, 2011)
4. Some people cannot dream
Some say that they don’t have dreams, but in all likelihood they do, it’s just that they don’t remember their dreams because they are heavy sleepers.
There are some people, though, who genuinely cannot dream.
Often as a result of brain damage from strokes, these patients can be awoken repeatedly during the night and asked about their dreams: they claim never to be dreaming (Bischof & Bassetti, 2004).
5. The purpose of dreams
Of course we don’t know what dreams are for.
It could be that dreams have no purpose, but are merely distracting by-products of losing consciousness in the particular way we do when we sleep.
Being human, though, means searching for explanations, so there’s no shortage of theories about what dreams are for.
They may be for testing out ideas, they may be for consolidating information, they may allow us to work on problems while we sleep, or they may be a way of getting rid of all the emotions we’ve built up during the day.
Which you believe probably has less to do with science than your own personal preference. So, believe whatever makes life more fun for you!
6. Myth: dreaming only occurs in REM sleep
Since the 1950s it’s been thought that dreaming is only associated with the so-called ‘Rapid Eye Movement’ portions of sleep, which make up around 20-25% of total sleep-time.
But this idea has now been challenged.
Studies have found that sometimes when people are awakened from REM sleep they report no dreams. And, sometimes when awakened from non-REM sleep they do report dreams (e.g. Nielsen, 2000).
Although much of our dreaming is done in REM sleep, some is probably also done in non-REM sleep.
7. People everywhere dream about the same stuff
A study of 50,000 dream reports by US psychologist Calvin S. Hall and colleagues found that there are remarkable similarities in the way people dream all around the world:
- Dreams are usually phantasmagoric: people, places, events and objects tend to merge into one another.
- The most common emotion experienced in dreams is anxiety and negative emotions are much more prevalent than positive.
- The vast majority of people dream in colour–if you watched monochrome TV growing up, though, you’re more likely to dream in black-and-white.
- Only around 10% of dreams are sexual in nature, although the percentage is higher amongst adolescents.
8. What do dreams mean?
At least I personally don’t believe dreams mean anything in the sense that most people understand this question.
But I’m in the minority, as demonstrated by a study which found that 56% of Americans endorse the Freudian view of dreams, in that they reveal deep psychological truths about the self (Morewedge & Norton, 2009).
Indeed this may even be an underestimate of how much store people put by dreams.
Morewedge and Norton’s study found that the majority of people think their dreams will influence their waking life, often more so than a similar waking thought.
So apparently I’m wrong: dreams mean a lot to people–even if it’s only because of the importance people ascribe to them.
→ Read the full study: The Over-Interpretation of Dreams.
9. Recording a lucid dream
Recording what happens in the brain during a particular dream is hard.
You can put people inside brain scanners while they’re asleep and then ask them afterwards what they dreamed about, but the problem is they don’t know when they dreamed it.
So it ends up being tricky matching up the brain imaging results with a particular dream.
One solution is to use lucid dreamers. These are people who have trained themselves to be aware of when they are dreaming and who can also take control of their dreams.
A recent study which used lucid dreamers this way found significant overlaps between the activity in the brain during wakefulness and during sleep (Dresler et al., 2011).
One of the authors, Michael Czisch, explained:
“Our dreams are therefore not a ‘sleep cinema’ in which we merely observe an event passively, but involve activity in the regions of the brain that are relevant to the dream content.”
10. Do blind people ‘see’ in their dreams?
Have you ever wondered if blind people can see in their dreams?
This is a question blind people get asked a fair amount.
Here is Youtube star, radio presenter and ‘blind film critic’, Tommy Edison, explaining the answer:
Studies back this up, finding that people who never had sight or who lost their sight before they were five do not dream visually.
Image credit: Simon Pais-Thomas