An observant Jewish friend told me she has recurring dreams about being caught unprepared for Shabbat.
(Shabbat is the Jewish Sabbath, celebrated every Saturday, when observant Jews are forbidden to work, carry things outdoors, spend money, use electrical devices, etc.)
She said that in the dreams, she would be out driving, far from home, and realize that Shabbat was due to begin in a few minutes, with no way to make it home or get a hotel in time.
I found this interesting because my recurring dreams are usually things like being caught unprepared for a homework assignment I have due tomorrow, or realizing I have to catch a plane flight but I’m not packed and don’t have a plan to get to the airport.
Most people attribute recurring nightmares to “fear”. My friend is “afraid” of violating Shabbat; childhood me was “afraid” of having the assignment due the next day. This seems wrong to me. Childhood me was afraid of monsters in the closet; adult me is afraid of heart attacks, something happening to my family, and AI. But I don’t have nightmares about any of these things, just homework assignments and plane flights.
So maybe the “unprepared” aspect is more important. Here’s a story that makes sense to me: what if recurring dreams are related to prospective memory?
Prospective memory is the form of memory you use to remember that something’s coming up and you need to prepare for it. For example, your teacher says “you have a homework project due on December 1”. More responsible people might write that down on a calendar or in a planner or something, but I always just winged it. Every few days, my brain would remind me, “You know you have a homework project due on December 1, right?” and then eventually I would grudgingly start working on it, and my brain would say “You remember you have to be done by December 1, right?” and then I would work harder.
How does this work? You’d have to have some kind of brain cell or whatever on a dedicated loop, checking every few hours to see if there’s a homework assignment you’ve forgotten about. This isn’t just the much easier task of answering “yes” if someone asks you whether you have an assignment. This requires constantly the brain cell to constantly ping memory to see whether there’s something that’s being forgotten.
What if that brain cell is still there? What if, every few hours, it keeps thinking “Oh no, I hope there isn’t a homework assignment I’ve forgotten about, better sift through my memory and see”. And during the day, my brain is functional enough to bar such useless thoughts from my consciousness, but at when my guard is down and there’s nothing else to think about, sometimes it gets through? And what if the dreaming brain uses that as the nucleus for a story?
This explains my friend’s Shabbat dreams, my homework dreams, and my forgotten-plane-flight dreams. What other categories of dreams does it explain?
Big test today I forgot to study for: This is a trivial extension of the homework example. I don’t really have these because I found tests less scary than homework and didn’t really keep track of them as much.
Enrolled in a class I forgot existed for months and now it’s the end of the year and I’m going to fail it: Presumably your prospective memory has to remember to go to the right series of classes every day at school.
Giving a speech in your underwear: This one doesn’t fit the theory, unless maybe the prospective memory task is “getting dressed”. This is, in some sense, a very important prospective memory task! I guess there does have to be some brain subroutine monitoring whether I’m dressed every time I go outside, and it’s just so fluid that I never think about it. But at that level you could explain anything, so I’m skeptical.
Flying: I don’t think my theory can explain this. I’ve heard claims that it’s because muscle feedback is blocked during REM sleep, so you feel weightless. I rarely have pure flying dreams, but I often have dreams about finding I can jump very high, glide, or otherwise come close. I don’t know if the muscle feedback theory predicts this.
Teeth falling out: I originally thought this might be related to brushing your teeth - one of the most common and important prospective memory tasks. But this doesn’t really make sense - you’d expect dreams about leaving home and suddenly realizing that you forgot to brush your teeth; the link to “teeth falling out” is psychologically tenuous. And these people note there are tooth-falling-out dreams in the Talmud; even though Talmud-era Persia had a little dental hygiene, I have trouble believing that a culture-bound dream could last that long. Some researchers did a study and found tooth dreams were linked to dental irritation symptoms during the day, so it’s probably the same as the flying dreams - your unconscious using weird sensations as the nucleus for a story. Sleep bruxism is a common condition that could cause unusual nighttime tooth sensations, although the researchers disappointingly weren’t able to come up with a specific link there.
So I think there’s some support for the prospective memory theory, but even more for a theory of “dreams that are based on weird sensations you have during sleep are likely to recur”.
Is there any way to fit the Shabbat/homework/plane-flight dreams into a “weird sensations you have during sleep” theory? I think you’d have to go with “you feel anxious during sleep, and those are the situations your brain comes up with where anxious is justified”. The reason you don’t dream about closet monsters or unfriendly AI is presumably that you haven’t experienced these things, and your brain doesn’t naturally think of them as a likely cause of anxiety.
I don’t find this entirely compelling, because I don’t think “For the whole semester, I half-forgot that I was taking a math class, and now I’m finally being forced to confront it, and all the other students are so far ahead of me that I can never catch up” is a simple natural experience which it makes sense to leap to as a cause of anxiety. The most common stressful experiences I have regularly - patients having emergencies, babies being inconsolable, people trying to cancel me online - almost never show up in my dreams. On the other hand, I do sometimes have dreams about fights with my parents, so maybe it has to be a stressful experience from my childhood in particular. But then why do I have so many dreams about missing airplanes, which wasn’t something childhood-me had to deal with? And when I asked about this on the ACX survey, it looked like childhood themes in dreams were less common than adult themes:
So I think there’s strong evidence for a somatic-sensation-nucleus theory of recurring dreams, and weaker but still-intriguing evidence for a prospective-memory-based one.
