Why Your Memory Changes a Little Every Time You Use It

Most of us treat memory like a filing cabinet: something happens, it gets written down, and remembering means walking back to the drawer and pulling out the page. The picture is intuitive and wrong in ways that affect how much weight you should give your own recollections, especially the ones you feel most sure about.

Recalling a memory looks a lot more like rebuilding something from parts than opening a file, and the rebuild can quietly pick up material that was never in the original.

Every time you remember something, you get a chance to edit it

When you bring a memory to mind it becomes briefly unstable before it's stored again, a process researchers call reconsolidation, and while it's unstable it can be changed. Your mood in that moment, what you've learned since, and the words you happen to use to describe it can all be folded in without you noticing.

A memory you've revisited many times is therefore closer to a photocopy of a photocopy than to a pristine original, with each pass adding small changes that become the starting point for the next one. The stories you tell most often can end up among your least reliable, which runs against the instinct that practice should make them sharper.

Feeling certain tells you very little

How sure you feel about a memory has only a loose relationship with how accurate it is. Vivid, detailed, emotionally charged memories feel authoritative for exactly those reasons, and they can still be substantially wrong.

The clearest evidence comes from flashbulb memory studies, where people were asked soon after a major public event how they'd heard the news and then asked again years later. Their accounts shifted a great deal while their confidence stayed high, and some people insisted on details that contradicted what they'd written down at the time.

Nothing about that points to a flaw in particular people, since the system behaves the same way in everyone.

Memory takes suggestions easily

Elizabeth Loftus showed how readily recollection bends to the wording of a question. Participants who watched the same footage of a car accident gave higher speed estimates when asked how fast the cars were going when they "smashed into" each other than when they "hit" each other, and they were more likely to report broken glass that was never there.

Later studies went further and found that, with suggestion and repetition, a proportion of people come to remember events that never happened, sometimes in rich detail and with real emotion. The work changed how courts treat eyewitness testimony and remains among the most consequential findings in psychology.

A memory built for the future has no need to be a recording

If memory were meant to be a recording device, all of this would count as failure. The picture changes once you see memory as a system that supports future decisions, because a working model of the world that takes in new information serves you better than one frozen at the moment it was made.

The gist of an event tends to be preserved well while the details are treated as expendable, which for most purposes they are.

What it means on an ordinary day

• Two people can remember the same argument completely differently, both honestly, with neither of them lying
• Notes written at the time beat recollection comfortably, so anything that might be disputed later is worth writing down that day
• Going over a grievance again and again can sharpen and distort it at once, because every retelling is another edit
• Childhood memories are especially unreliable, since many of them are partly assembled from photographs and family stories
• Certainty isn't evidence, however much it feels like it should be

Some memories hold up better than others

A few things do improve reliability. A note made close to the event is the big one, and memories you've rarely discussed hold up better than well-worn ones because they've had fewer chances to be revised. Details that were central to the event also survive better than the scenery around them.

Corroboration helps as well, provided it comes from someone who wasn't part of the same retellings, since shared storytelling can bring two accounts into agreement without making either one accurate.

The editable window can also be used on purpose

Reconsolidation isn't only a source of error. Because a memory becomes modifiable when it's reactivated, several trauma treatments work partly on that principle by bringing a memory to mind under conditions of safety, so that what gets stored afterwards carries less of the original charge.

That's one reason effective trauma therapy involves approaching a difficult memory rather than steering around it, and why it's done carefully and with support. Sitting alone with distressing material and hoping for the best doesn't create those conditions.

If difficult memories are intruding on your day or shaping decisions you'd rather they didn't, our psychologists work with trauma and acute stress at our St Kilda clinic and via telehealth, and you can read about our approach to individual therapy. If you're in distress right now, Lifeline is available on 13 11 14.