The science of memory:

A few unforgettable facts about the way your brain remembers.

Unforgettable facts about the way your brain remembers

In an essay published towards the end of his life, titled “Speak, Memory”, renowned British neurologist Oliver Sacks describes the shock he felt upon finding out that one of the most vivid memories of his early childhood was false. Sacks remembered a thermite bomb falling behind his house during The Blitz – a German bombing campaign against London during the winter of 1940 and 1941 – and recalled his brother and father using pails of water to try and extinguish the device. But after chatting to an older brother, he realised he hadn’t even been present in London at the time the bomb was dropped. He had constructed the memory from a vividly descriptive letter sent by another brother, who had witnessed the bomb landing.

"How could my brother dispute a memory I would not hesitate to swear on in a court of law, and had never doubted as real?" Sacks wondered. This experience of coming to doubt one's own memories is very common, especially regarding events that happened in early childhood. From Sacks' account, we can see two things: firstly, that our memories are emotional and changeable, much like a poorly trained puppy; and secondly, that other people can make our memories for us, without us even realising it's happening.

Maybe because we like to think of our brains as little beep-boop flesh computers, we tend to consider memory like a kind of biological recording device – one that makes exact, replayable copies of events. And it is – sort of. "A typical memory is really just a reactivation of connections between different parts of your brain that were active at some previous time," says neuroscientist Nikolay Kukushkin. Lots of those connections have to do with emotion – both how we felt at the time the memory was originally stored, and how it made us feel to recall it after the fact. So, we don’t just dig up the exact same memory over and over – the act of remembering can actually change the memory itself.

As for those bogus childhood recollections? Researchers from the Centre for Memory and Law at City, University of London, did their own study into people's earliest memories. Reinforcing Sacks’ experience, they found many folks ‘remembered’ experiences from their infancy – around the age of one or two – that probably didn’t happen. We actually start forming more concrete memories at about three or four years old, and before that point, we have what’s called ‘infantile amnesia’ – an inability to retrieve memories connected to specific situations or events. Babies may be cuter than adults, but their brains are a lot mushier. The fact is, our first few years are one big memory black hole.

So why, then, do those early memories feel so vivid? The Centre’s researchers concluded that they’re probably a result of other people describing things to us, or even spotting a scene in an old photo album. According to the study’s co-author, Martin Conway, "This type of memory could have resulted from someone saying something like, 'Mother had a large green pram.' The person then imagines what it would have looked like.” Over time, these snippets of information become what feels like a real recollection, and we start to add extra details of our own. So, your ‘first memory’ of eating chopped-up fruit on your nan’s back porch as a wee one may have happened, but probably not as you picture it – sorry.

Our memories are not only influenced by our own tellings and retellings, but also those of other people. Everyone you know has probably, at some point, used their grubby little memory-mitts

to mess around with your brain. ‘Collective memories’, contributed to and shared by friends, families, neighbourhoods and even whole countries or continents, are in a constant process of exchange and dialogue. Now, excuse me while I fashion myself an attractive little tinfoil hat.

And let’s not forget about forgetting. Humans might have bigger brains than most other animals, but there’s only so much you can cram in there before our heads start creaking and warping like filing cabinets stuffed with too much paperwork. A little bit of a clean out every now and then can actually improve our decision-making processes. University of Toronto boffins Blake Richards and Paul Frankland discovered that a lot of the work our memory does is deciding which recollections we can safely get rid of, which is probably why I’ve forgotten at least 90 per cent of the times I’ve done something really embarrassing. Thanks, brain! Less thanks for the one billion times I have forgotten my online banking login.

This is another way that memory is less like a recording device and more like a scrapbook. Your brain isn’t just going for accuracy; it’s ranking things by importance, too. One of the tools your brain uses to decide whether you need to remember walking out of the loos with your skirt tucked into your undies is dreaming. In her book The Secret World of Sleep, neuroscientist Penelope A. Lewis says that snippets of the day people have just experienced show up in 65 to 70 per cent of dream reports. We don’t really know how dreams help us process memories, especially because most people don’t even remember their dreams, but it seems clear that our brain doesn’t just show us those weird sleep-movies to keep us entertained while we’re unconscious. Despite knowing so little about how memory works, humans are well on the way to being able to tinker with it like the mad scientists we truly are. For instance, researchers from the Weizmann Institute of Science in Israel have used tiny pulses of light to activate neural pathways in mouse brains, effectively erasing fearful memories in the mice. Elsewhere, research teams have used sound, specialised talk therapy and other interventions to try and weaken or deactivate negative recollections.

This kind of technology could have lots of exciting clinical applications, especially for people whose memories are so intrusive that they interfere with everyday life, as in cases of post-traumatic stress disorder. Eye movement desensitisation and reprocessing, or EMDR, is a kind of psychotherapy where people recall traumatic memories while engaging in a bilateral sensory activity, like moving their eyes back and forth, or listening to a special type of side-to-side sound recording through headphones. It’s unclear exactly why it works, but the combination of recall and stimulus seems to significantly lessen how awful it is to summon up the memory after therapy. It doesn’t delete memories completely, but it gives the brain a helping hand to change them into something less scary. The textures of memory are key to who we are, not just as single people, but as a species continually learning to live with each other in the world. As Sacks says in his essay, "Memory is dialogic and arises not only from direct experience, but from the intercourse of many minds." Basically, it’s emotional and fallible, and it’s also not set in stone – we have more control over it than we may think. Memory belongs, in a very real sense, to all of us, and that gives it far more power than is obvious at first glance. And that's really worth remembering.