Ask Discover: Why Don’t We Know When We’re Dreaming?

By Neuroskeptic | August 1, 2013 12:17 pm

Got a burning science question? Send it to and we’ll try to answer it here or in a future issue of the magazine.

The print version of Discover Magazine has a new feature called Ask Discover, where readers’ questions are answered by one of the bloggers. In the current issue, Alan Schertzer asked:

Why don’t we know when we’re dreaming, especially when we interact with dead characters? My dad died a long time ago, yet when he inhabits my dreams, it seems perfectly normal. Do we all become morons when dreaming?

You can find my brief answer in the printed magazine, but here’s a slightly longer take.


This is a very good question. Dreams are, literally, an everyday experience but they are, when you think about it, extremely puzzling things. The topic of dreams touches on some of the deepest problems in neuroscience: the self, memory, and self-awareness. Even the question of why dreams happen is hotly debated.

In dreams, we often have bizarre experiences that seem perfectly normal at the time. We do not realize that what’s going on is impossible. This may be because in dreams we rarely reflect on our own experiences, thoughts, or self.

However, occasionally, people do become aware that they are in a dream: this is called lucid dreaming. It happens to many people from time to time (I can recall four or five lucid dreams, myself, mostly in childhood). With training, some people are able to achieve lucidity more often.

The essence of a lucid dream is self-awareness. So lucidity could offer neuroscientists a window onto the nature of dream unawareness.

In normal dreams, some areas of the brain are less active than when we’re awake. In particular, activity in the precuneus, part of the medial parietal lobe, is lower.

The precuneus is activated during selfreflective experience as well as being a hub of the ‘default mode network‘. This is a set of brain areas that’s active ‘by default’ when we’re awake – although it’s deactivated whenever we’re engaged in an external activity or task that demands attention.

In one small study, activity in the precuneus was higher during lucid dreams than in normal ones. So the precuneus, and connected areas, might be responsible for the insight that’s often lacking in dreams. An analogy might be that dreams are like a dramatic, attention-grabbing external event that leaves us ‘no time to think’ about ourselves or what it means.

But how this actually happens is unknown. There is evidence that something in the precuneus is at work, but we don’t yet know how the millions of neurons in this area can give us waking self-awareness, or how dreams switch this off.

CATEGORIZED UNDER: Ask Discover, blogging, science, select, you
  • djlewis

    The oddest part of this post is that it appears to assume that neuroscience is not only the main source of knowledge about dreams, but the *only* one worth considering. In fact, it would be easy to prove that what neuroscience knows (in any reasonable sense of “know”) about dreams scarcely amounts to a thimbleful of the ocean. This piece, therefore represents a distinct, philosophical assumption that includes naive/scientific materialism, but goes much further, to a full-throated rejection of all thinking about dreams prior to the invention of the fMRI. That sort of assumption is, in a nutshell, what the “skeptic” in “Neuroskeptic” should be about, IMHO. But it is, alas, far from that, despite the final, finally candid though vastly understated paragraph.

    • Chaorder Gradient

      well first they had to make the whole concept of dream analysis provoke absurd notions of phalusses as freud did such a good job of

    • Neuroskeptic

      If you have any actual suggestions as to what I should have included, I’d love to hear them.

      • Douglas J. Bender

        Spiritual and moral realities that might be at the heart of why we dream. If we ARE created beings (and we are), then our Creator may very well have chosen dreams to provide a way to “teach” or reveal to us certain things that we, in our conscious state, will not dwell upon or easily comprehend. This is at least one possibility for the purpose of dreams (and not an exclusive one, at that).

        • Koroma Matthieu

          I comment for the first time on discovery because some comments here and the one on Freud below hurt.
          @Neuroskeptic:disqus thanks for this informative article. For a good review on dreams, if I may, i would advice the part on dreaming of Toward an integrative theory of sleep and dreaming,
          Amir Muzur (2004) which provides interesting insight with evolutionary considerations (but does not answer the question :) )

        • StarCityFan

          That’s a possibility, but it’s not exactly a scientific one. How would you prove (or disprove) it?

          • Douglas J. Bender

            I’m not sure, but I think it’s at least as “scientific” as the “Big Bang Theory” and “Multiverses”. I suppose one could do some tests to determine content of some dreams, and see if the evidence corresponds with the theory to any degree.

          • LukeyL

            The big bang theory has plenty of evidence in its favor. It predicted, for example, the existence of cosmic microwave background radiation, and we found exactly that. As far as multiverses go, you’re correct that that is simply an interpretation of quantum mechanics that does not presently have any evidence in its favor (that I know of – I’m not entirely up to date on the latest and greatest) – but at the same time, any scientist you ask worth his or her salt will tell you exactly as much.

          • Douglas J. Bender

            Thank you for confirming my claim regarding “Multiverses”. And as far as the “Big Bang Theory is concerned, there are quite a few problems with it, some sufficiently irreconcilable that if it wasn’t such an important theory for atheists, it would have been discredited and discarded long ago. Please consider the following article regarding the “Cosmic Microwave Background”: . And if you have a chance, and are willing to be objective and listen to the “opposing” side, please read or peruse “Dismantling the Big Bang”.

          • Brandon Michael

            It’s funny someone would ask how could you prove or disprove it…When the scientific community just lobs theories and conjecture much the same.

          • StarCityFan

            Plenty of scientific hypotheses get lobbed, but almost all of them get shot down pretty quickly.

      • Tijms

        You could have included some work by Stickgold on the phenomenology of dreams in relation to daytime task activity, maybe throw rodent replay mechanisms and memory consolidation into the mix.

        Then, you could have mentioned synaptic pruning theories and maybe Friston’s idea that in dreaming, Bayesian priors are being updated without testing them against sensory evidence, hence the process of “reality checking” is bypassed.

        I think these issues, methodologically spanning cognitive science to psychology to cognitive neuroscience to neurobiology, would have given a fairer idea of the state of research. But it would be a complicated post to write, so I actually like your single-experiment approach here.

    • Wouter

      “The oddest part of this post is that it appears to assume that neuroscience is not only the main source of knowledge about dreams, but the *only* one worth considering.”

      It’s definitely not the only source available, but without doubt the only one worth considering. What other part of science outside neuroscience, which concerns the structure and function of the nervous system and brain, is there that in principle is able to measure dreams objectively? None, as far as I know, but that maybe due to naive/scientific materialism. Perhaps, you could enlighten us, as to what other organ or “force” causes dreams to exist.

  • Norma Frank

    It seems odd to me that this interesting and (to me, at least) informative answer would provoke such a rude response. Without it, I would have just read it and thought “That’s interesting” but not commented.

  • DCO

    This is decidedly unscientific, but I like to think that the reason dreams seem so real is because they are. I like to think that when we dream, our consciousness shifts its focus from this physical reality to one of the many (possibly even infinite) other alternative universes that could theoretically exist that we could be simultaneously inhabiting. Each dream could be a look into a different one of these universes, each with slightly different physical laws and outcomes to random events that have produced universes similar enough to our own that our existence is possible. This of course also requires one to believe that the brain is not the source of consciousness, but if you perceive the brain as more of a transceiver akin to a wifi enabled device you control remotely then it becomes easier to conceive of this possibility. Obviously there is no way to prove this and thus lies purely in the realm of philosophy, but I personally find it a more comforting step-brother to quantum suicide theory.

    • Jayant mharolkar

      Your thesis is very interesting.

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  • Fred Hill

    I think one of the bizzare things about dreams, is we don’t know how long we’ve been dreaming while dreaming before we actually realize “Holy Crap, this is a dream”…what’s also bizzare and actually crazy on my behalf Is, when I realize I’m dreaming, I know exactly what to do to get out of that dream, because for some special reason, I know from other times I dreamt, while having that dream, I know to escape it. It’s like I live a totally different life in my dreams, and I’m able to think about the past during dreaming!

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Neuroskeptic is a British neuroscientist who takes a skeptical look at his own field, and beyond. His blog offers a look at the latest developments in neuroscience, psychiatry and psychology through a critical lens.


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