By Graham Duggan  

How well do you remember your family vacations from when you were young? How about your first date, or learning to ride a bike? Do you know where you were when you heard about the 9/11 attacks or the death of Princess Diana? You are likely nodding your head — “yes, I remember very clearly.”

Chances are, you’re wrong.

In the Nature of Things documentary The Memory Mirage, scientists explain just how much our memories can deceive us. We used to think that our experiences were recorded in our brains like a videotape which we could play back. However, we’re finding that memories are more often written in water — meaning our life experiences probably didn’t happen exactly how we remember them.

We can’t even remember key events in our own lives

Why do two people remember the same event differently? New science is showing us how our memories are vulnerable to change over time.

In the days following 9/11, cognitive neuroscientist Elizabeth Phelps surveyed over 3,000 subjects, asking them what they recalled about that day — where they were, who were they with, and how they heard the news. One year later, she asked them the same questions, and again at 3 and 10 years on. After just one year, many of the answers changed. When first asked, a subject was perhaps in a café with a friend when they heard the news. The following year, they were certain they were alone at home.

These are called “flashbulb” memories — shocking experiences that are stored vividly in our brains, capturing the context and emotional reaction to the event. However, apart from the central incident itself, the other details of the memory are easily altered.

Each time we recall a memory, we only remember the last time we recalled that memory. And each time we pull up a memory, we may introduce new details that never occurred in real life.

Eyewitness testimonies are often wrong

When it comes to solving crimes, police have traditionally relied on eyewitness accounts to catch criminals — who better to finger a criminal? But researchers featured in The Memory Mirage show just how wrong we can be when relying on memories, even minutes after the event.

When Jennifer Thompson was assaulted at the age of 22, she was confident she identified the guilty man after carefully memorizing every detail of her attacker. After spending 11 years in prison, the convicted man, Ronald Cotton, was proven innocent through new DNA evidence — Thompson had identified the wrong person.

Incorrect memories from eyewitnesses may have led to the wrongful convictions of thousands of innocent people across North America. Through DNA analysis, 350 criminal cases have been overturned, and in 245 of those cases, eyewitnesses had ID’d the wrong person.

All of our memories are vulnerable to change, especially in their early stages. That means that the memories of eyewitnesses can be quickly altered through positive reinforcement during the investigative and judicial process. Police can inadvertently implant false details in eyewitness memories that weren’t there at the time of the crime.

Following his release, Cotton worked together with Thompson to pass legislation requiring reforms to eyewitness testimony.  They succeeded in North Carolina, and since then, twenty other states have followed. Canada has had similar guidelines since 2001, but they’re not always used.

Inception is real — false memories are easy to implant

With growing evidence of how memories can trick us, researchers have tried bold new experiments to find out if they could implant a false memory and have someone believe it was true.

Canadian scientist Julia Shaw suggested to her subjects, UBC university students that they had a minor run-in with police as teenagers, incidents that never happened in real life. Of course, they didn’t remember the event at first, but when offered a “guided imagery technique,” said to help retrieve lost memories, the students began to reveal details. By their third interview, 70% of the students recalled the fake incident, some describing it in detail.

MRI scans show that false memories are indistinguishable from real ones. As far as the brain is concerned, the false memory actually happened.

Faulty memories make us happier

It’s clear that the human brain is wired to forget details. But why?

Researchers report that people diagnosed with depression may remember negative experiences more accurately than the rest of us. But remembering both the good and the bad can negatively affect emotion and poison the present.  Memories that can be reshaped allow us to reinterpret negative events with positive outcomes. It appears that forgetting the details helps protect our mood and self-esteem. 

MORE:
We change our memories each time we recall them, but that doesn’t mean we’re lying
Total recall: some people can remember every day like it was yesterday

For more Watch The Memory Mirage on The Nature of Things

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