Or could you? You all possess the name and history, but the fact is that you’re all somewhat different people, in possession of different values and goals. And your life’s memories might have less in common than expected. Your memory of who you were at fifteen is different to who you actually were at fifteen; moreover, you’ll have different memories that relate back to the same events. Why? Because of what a memory is – and isn’t.
Imagine a person could be split into herself at all her different ages. Would they all agree on the same memories? If not, are they really the same person?
Rather than memory being an accurate video recording of a moment in your life, it is a fragile brain state from a bygone time that must be resurrected for you to remember.
Here’s an example: you’re at a restaurant for a friend’s birthday. Everything you experience triggers particular patterns of activity in your brain. For example, there’s a particular pattern of activity sparked into life by the conversation between your friends. Another pattern is activated by the smell of the coffee; yet another by the taste of a delicious little French cake. The fact that the waiter puts his thumb in your cup is another memorable detail, represented by a different configuration of neurons firing. All of these constellations become linked with one another in a vast associative network of neurons that the hippocampus replays, over and over, until the associations become fixed. The neurons that are active at the same time will establish stronger connections between them: cells that fire together, wire together. The resulting network is the unique signature of the event, and it represents your memory of the birthday dinner.
Your memory of an event is represented by the unique constellation of cells involved in the details you experience.
Now let’s imagine that six months later you taste one of those little French cakes, just like the one you tasted at the birthday party. This very specific key can unlock the whole web of associations. The original constellation lights up, like the lights of a city switching on. And suddenly you’re back in that memory.
Although we don’t always realize it, the memory is not as rich as you might have expected. You know that your friends were there. He must have been wearing a suit, because he always wears a suit. And she was wearing a blue shirt. Or maybe it was purple? It might have been green. If you really probe the memory, you’ll realize that you can’t remember the details of any of the other diners at the restaurant, even though the place was full.
So your memory of the birthday meal has started to fade. Why? For a start, you have a finite number of neurons, and they are all required to multitask. Each neuron participates in different constellations at different times. Your neurons operate in a dynamic matrix of shifting relationships, and heavy demand is continually placed on them to wire with others. So your memory of the birthday dinner has become muddied, as those “birthday” neurons have been co-opted to participate in other memory networks. The enemy of memory isn’t time; it’s other memories. Each new event needs to establish new relationships among a finite number of neurons. The surprise is that a faded memory doesn’t seem faded to you. You feel, or at least assume, that the full picture is there.
And your memory of the event is even more dubious. Say that in the intervening year since the dinner, your two friends have split up. Thinking back on the dinner, you might now misremember sensing red flags. Wasn’t he more quiet than usual that night? Weren’t there moments of awkward silence between the two? Well, it will be difficult to know for certain, because the knowledge that’s in your network now changes the memory that corresponds to then. You can’t help but have your present color your past. So a single event may be perceived somewhat differently by you at different stages in your life.
The fallibility of memory
Clues to the malleability of our memory come from the pioneering work of Professor Elizabeth Loftus at University of California, Irvine. She transformed the field of memory research by showing how susceptible memories are.
Loftus devised an experiment in which she invited volunteers to watch films of car crashes, and then asked them a series of questions to test what they remembered. The questions she asked influenced the answers she received. She explains: “When I asked how fast were the cars going when they hit each other, versus how fast were the cars going when they smashed into each other, witnesses give different estimates of speed. They thought the cars were going faster when I used the word smashed.” Intrigued by the way that leading questions could contaminate memory, she decided to go further.
Would it be possible to implant entirely false memories? To find out, she recruited a selection of participants, and had her team contact their families to get information about events in their past. Armed with this information, the researchers put together four stories about each participant’s childhood. Three were true. The fourth story contained plausible information, but was entirely made up. The fourth story was about getting lost in a shopping mall as a child, being found by a kind elderly person, and finally being reunited with a parent.
In a series of interviews, participants were told the four stories. At least a quarter claimed they could remember the incident of being lost in the mall – even though it hadn’t actually happened. And it didn’t stop there. Loftus explains: “They may start to remember a little bit about it. But when they come back a week later, they’re starting to remember more. Maybe they’ll talk about the older woman, who rescued them.” Over time, more and more detail crept into the false memory: “The old lady was wearing this crazy hat”; “I had my favorite toy with me”; “My mom was so mad”.
So not only was it possible to implant false new memories in the brain, but people embraced and embellished them, unknowingly weaving fantasy into the fabric of their identity.
We’re all susceptible to this memory manipulation – even Loftus herself. As it turns out, when Elizabeth was a child, her mother had drowned in a swimming pool. Years later, a conversation with a relative brought out an extraordinary fact: that Elizabeth had been the one to find her mother’s body in the pool. That news came as a shock to her; she hadn’t known that, and in fact she didn’t believe it. But, she describes, “I went home from that birthday and I started to think: maybe I did. I started to think about other things that I did remember – like when the firemen came, they gave me oxygen. Maybe I needed the oxygen ’cause I was so upset that I found the body?” Soon, she could visualize her mother in the swimming pool.
But then her relative called to say he had made a mistake. It wasn’t the young Elizabeth after all who had found the body. It had been Elizabeth’s aunt. And that’s how Loftus had the opportunity to experience what it was like to possess her own false memory, richly detailed and deeply felt.
Our past is not a faithful record. Instead it’s a reconstruction, and sometimes it can border on mythology. When we review our life memories, we should do so with the awareness that not all the details are accurate. Some came from stories that people told us about ourselves; others were filled in with what we thought must have happened. So if your answer to who you are is based simply on your memories, that makes your identity something of a strange, ongoing, mutable narrative.
The aging brain
Today we’re living longer than at any point in human history – and this presents challenges for maintaining brain health. Diseases like Alzheimer’s and Parkinson’s attack our brain tissue, and with it, the essence of who we are.
But here’s the good news: in the same way that your environment and behavior shape your brain when you’re younger, they are just as important in your later years.
MEMORY OF THE FUTURE