We change our memories each time we recall them, but that doesn’t mean we’re lying

When I was a child, my grandfather often told me how he'd seen mutinying Russian soldiers from the battleship “Potemkin” march right by his house in Odessa, Russia in 1905 — one of the famed moments leading up to the Russian revolution.

It was a wonderfully colourful tale, but later in life, I realized he'd been less than a year old when it happened — not nearly old enough to mentally record these details. He'd obviously heard the tale from his parents so often it became part of his memory.

I’ve always wondered how my grandfather came to believe his own imagined memories — and it’s part of what led me to spend a year working on The Memory Mirage, a Nature of Things film that shows us that our memories are far more fragile and faulty than we ever thought.

Scientists have demonstrated that, as the years go by, much of what we think we remember is false. It seems our brains can't store every detail we experience, so we recall the gist of events — enough to create a story that makes sense to us. Every time we recall a story or tell it to others, we change small bits depending on whether our audience looks fascinated, or bored. Then the next time we retell it, we only remember the last version we told – and the errors compound as in a children’s game of broken telephone.

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Working on this film has made me look at historical accounts differently. CBS TV’s main nighttime anchor Brian Williams and Hillary Rodham Clinton were both accused of repeatedly lying about coming under military attack in foreign countries. Williams told stories about being under fire in a helicopter in Iraq; Clinton about when she was on a mission to Bosnia accompanied by the military. It was eventually revealed that neither person came under attack, they were both just visiting dangerous places where gunfire is a constant threat.

It was speculated that Williams and Clinton were both deliberately exaggerating their stories to enhance their public images. But now I wonder if they just retold and tweaked their war zone stories so many times they gradually came to believe them. Is it possible they both think they are telling the truth?

One scientist told us this happens to some war heroes on tour. They gradually enhance their exploits as they move from audience to audience, city to city, until the anecdote is so heroic it's barely recognizable.

Once our brain has a new version of a story, it forgets and erases the former versions. Even the most sophisticated MRI brain scans can't distinguish between truth and fiction when people believe what they're saying.

Closer to home, I’ve also learned it’s wise not to argue with my spouse about who-said-what-to-whom seven years ago. Science suggests that we’re probably both wrong about many events in our memory album. I should enjoy and bask in my memories, but not necessarily believe in their truth, any more than I do my grandfather’s colourful old tales.

Watch The Memory Mirage.