How Do We “Hear” In A Dream?

This is not my observation. It was made by Greek philosophers thousands of years ago, and it isn’t really that accurate as analogies go. For one thing, there are important differences between the experiences of those with psychosis and dreaming, especially as psychotic hallucinations tend to be auditory in nature, while dreaming is often mostly visual. However, dreamers can hear content in their dreams, so as a study from 2020 points out, the two mental states are not completely dissimilar.

Indeed, anyone who has experienced a hypnopompic hallucination, a vivid, dream-like experience that occurs when you’re waking up, or sleep paralysis will know how easily the lines between dreaming and hallucination can be.

But this highlights something interesting about the state of dreaming: how is it that we hear in our dreams? For instance, how can I have a conversation with, say, Elmo, Darwin, or a wizard (only one of these has appeared in my dream and I won’t say which) in a dream where I can both see and hear them, despite them not being physically present? The simple answer is that the brain is awesome, but let’s find out just how it works.

In essence, hearing in dreams is completely tied to how our brains process sensory information and create experiences while we sleep.

When we’re asleep, our bodies largely become immobile through a process known as muscle atonia, but our brains actually operate similarly to how they do when we are awake. This involves certain areas becoming more active while others start to shut down, depending on the stage of sleep. REM (rapid eye movement) sleep, the stage when we experience the most vivid dreams, is known to be a time of intense brain activity.

At this time, our brains shut down activity in specific regions associated with logic and reasoning, such as the frontal lobe (and especially the prefrontal cortex), as well as primary sensory input systems that detect external sensory information (basically sounds in the real world). At the same time, regions involved in memory and emotions (the cerebral cortex, hippocampus, and amygdala) become livelier, sending more messages.

But while sensory input is reduced, it is not completely stopped. Research into monkey brains has shown that, when they sleep, the areas responsible for auditory information processing also don’t shut down completely. This means that, while most sensory stimuli from the waking world do not register, some will be detected. So, sounds that you hear around you while you’re asleep, such as an alarm going off, a neighbour doing DIY early on a Sunday morning, or (in my experience) a pigeon cooing at your windowsill, can all be incorporated into the dream narrative.

However, if you hear something that is too jarring or loud, then the brain will wake you up as it interprets it as a potential threat.

But these are still sounds produced by external sources; they’re not produced by our brains on their own. What about sounds that are completely internal?

When we’re dreaming, our auditory cortex can simulate sound experiences, such as music, environmental noises, animal noises, voices, or other auditory features – even if there are none being produced externally. 

In the 2020 study mentioned above, the researchers found that, out of the admittedly small number of participants they examined, voices were the most common form of sound heard in a dream. They achieved this by asking 13 people who recorded their dreams upon waking; 83 percent of sounds identified were from people talking, while 60 percent involved the dreamer talking to someone else. Participants reported that the sounds were often clear and memorable, while some voices spoke in foreign languages, and others just laughed, screamed, or cheered.

This study, although small, represents one of very few to examine auditory impressions in dreams; the vast majority of research into dreaming has focused on its visual content.

Interestingly, it is possible that the brain creates these internal sounds from our memories. It seems that when we dream, our brains pull on past experiences to construct the auditory elements we hear. At the same time, activity in our limbic systems (include the amygdala and hippocampus), which regulate emotional content, contribute to fitting the sounds into our dream narratives and our reactions to them.

But why does it all feel/sound so real? Well, earlier I mentioned that when we sleep, our brains dial down activity in our frontal lobes. This area is responsible for logical reasoning and critical thinking, so our brains essentially turn down our ability to question the plausibility of a dream and its weird content. The activity in the amygdala also amplifies at this point, which adds emotional reactions to the dream narrative, making it feel more vivid.    

It must be stated that dreaming remains a complex and still relatively unknown area of research. It is an incredibly complicated phenomenon, and we are still learning how it is that our brains produce such incredible experiences. More information on the weird world of dreaming and science can be found here.