Yesterday, a stranger emailed me out of the blue — we will call him “Mark” — and he had a story to tell.
He’d been drifting off to sleep, listening to Dan Savage’s podcast, when he heard a woman being introduced — a woman, he realized with a jolt, with whom he’d had “a memorable conversation and makeout session on a couch in her DC apartment twenty-plus years ago.” He wrote to tell me that hearing me talk about the science of hypnosis, while in that trippy liminal state between wakefulness and sleep, was one of the more surreal experiences of his life.
This feels mean to say, but it’s true: I have absolutely no memory of this makeout session, or Mark’s entire existence, for that matter.
I am sure that Mark is a perfectly memorable guy, and probably an excellent makeout partner. The problem is me: I have something called SDAM -- Severely Deficient Autobiographical Memory. As a result, my brain recalls about a tenth of what normal people remember. But much more weirdly, my subjective experience of remembering is wildly different from most peoples’.
SDAM, by the way, is not a diagnosis — it’s just a description, invented by the scientist Brian Levine. Levine is famous for his work with the guy the “Memento” movie was based on — a man named Kent Cochrane. A motorcycle accident essentially obliterated Kent’s hippocampus — the deep brain structure responsible for tagging and coordinating the replay of memories. The result? He lost his episodic memory, but his semantic memory remained weirdly intact.
So, Kent remembered all the facts about himself and his life. What he lost was the ability to replay memories — to do the mental time travel Levine’s colleague Endel Tulving called “autonoetic consciousness.” That means, Kent knew his brother had gotten married, and that he attended the wedding. But all the juicy details — the fact that he surprised everyone by showing up with a big poufy perm, for instance, was lost.
Of course, the fact that he showed up with a perm is something that could be encoded in semantic memory, too. But episodic memory is much better at capturing juicy, atmospheric details of your life — things like what you wore, or what the weather was that day, or what you were thinking and feeling at the time.
You guys can do WHAT?
When you ask someone to reminisce about their past, it’s nearly impossible to tell which kind of memory system they are using — episodic or semantic. In fact, neurotypical people generally engage both systems: saying what happened (often semantic), and then using their episodic memory to replay the event and re-live the juicy sensory details — what you felt, saw, tasted and were thinking.
People like me — the SDAMers — we rely mostly on our semantic memory. That means, we’re all about the plot — what happened, the facts. That gives us an advantage when it comes to big-picture thinking — and it drains our pasts of a lot of their emotional power.
At the other end of the mnemonic spectrum are people with HSAM. They remember way too many details from their lives, certainly more than is practical. But, we as a culture find them very impressive — bringing them onto the Today Show and asking them what the weather was like on April 6, 2022.
(Hoda if you’re reading this: Call me. I’ll demonstrate my amazing ability to forget a makeout session — which is truly remarkable as the total number of people I’ve ever French kissed can be counted on one, maybe two hands.)
I am extremely impressed, floored really, by the fact that most other humans can replay moments from their past. Now, this is the point where people always say: OK, Sadie, but it’s not really that accurate… blah blah blah. Listen, I know all that research — I fully understand that your memory is way less reliable than it feels to you.
But let me tell you, from an outsider’s perspective, episodic memories are astonishingly accurate. Truly a marvel of biology.
If you don’t believe me, check out this fantastic paper by Levine and his colleagues. They had adults take an audio-guided tour of the Baycrest medical center, which is lovely by the way, full of light and art and actual living trees. Later, they asked the participants to freely recall what they saw — things like the names of artworks, their materials, their position in space, what they were thinking at the time. The participants generated dozens and dozens of details — and they were 90% accurate.
Levine then polled memory researchers and asked them to predict how accurate the participants would be. Their guess? 50%
Friends, I took this tour. And I remember NOTHING about it. I remember THAT I took the tour, that there was an audio narrator, and a scale model of the building, and at one point, I accidentally skipped a track. I recall being told to take note of the number of chairs in a room that was raised up and to the left of me. This is a total of 8 details to the neurotypical average of 100.
Someone could be mentally making out with me RIGHT NOW
What’s really boggling my mind the fact that neurotypical people are able to almost re-live moments from their pasts! These research participants were going on the tour again, seeing what they saw before — which, I’ve been told, feels like either a video or a full-blown immersive experience.
If Mark is one of the “full-blown immersive experience” guys, that means that he gets to make out with me again, whenever he wants! From his description, however, his memory sounds more semantic than episodic: He recalled what we talked about (that I’m from Florida, the general concept of hypnosis.) If he remembers other things — the texture of my couch (velvet), the smell of my breath (usually peanut butter), what it felt like to kiss me — he was too polite to say.
Reader, I apparently have a whole life out there. I was places, with people, and things happened that meant something.
I just have to take their word for it.
I am, to be honest, a little jealous. It seems that I’m missing out on a large part of the human experience.
But what can you do? My brain is literally built this way. Levine scanned me, and found my left hippocampus is bigger than my right, especially in the fornix, the hippocampus’s primary output pathway. Most people have the opposite asymmetry, because they are remembering things visually — a right-hemisphere specialty. Me? I am remembering things in words — the exclusive domain of the left half of your brain.
It’s a subtle physiological difference, nothing like K.C. ‘s obliterated hippocampi, but it seems that my brain was built to be extremely word focused and rather abstract. I am great at getting the gist of things. I am terrible at recalling the details.
And maybe that’s what I’ve finally come to appreciate about other people’s memories. I can’t revisit most of my past. But other people can.
They remember conversations I don’t. Dinners. Road trips. Entire relationships. Taken together, they form a kind of distributed backup drive for my life.
So thank you, Mark, for returning a little piece of mine.
I think some people would like a targeted or even era-spanning version of this. If someone could zap a decade of cringey memories from my life and render them text I could put on a page, I'd be happy, and may wonder "so how do we explain what happened next?" but at least the "next" would be naturally forgotten as important, which was how it felt at the time, but our collective understanding of how eras in a life go, it really wasn't.
If that were a drug, it should be named Desaturation.