Do you often forget things? Wish you had a better memory? Me too. But there’s a far more sinister way your memory may be failing you. Being positive you remember an event is actually no guarantee it ever happened.

Could you be fooled into believing you had taken a ride on this balloon? Balloon image credit Jayson via Flickr

Your memory is fickle

It’s tempting to think our memories work like video recorders: faithfully recording our surroundings, thoughts and feelings. We can accept our brains might not have room for everything, so we end up holding onto only the most important, or traumatic, or embarrassing bits. But do our brains sometimes make up entirely fictional memories? Yes, indeed they do.

It’s not surprising that our recollections of past events can be hazy and that we get small details wrong. For example, seven weeks after the event itself, a researcher asked people about their memories of September 11, 2001. Among other questions, was “on September 11th, did you see the videotape on television of the first plane striking the first tower?” Three-quarters were confident they remembered watching the footage on that day. Seems reasonable, except that the footage wasn’t actually aired until a day later. A tiny detail, but a good illustration of the way we misremember events.

Research has shown we constantly fill in the gaps between real pieces of memory, and along the way we make assumptions, and plenty of mistakes. We construct our memories, without even being aware we’re doing it. Emotional memories may be more accurate, but no memories are immune to contamination. Memories that are not quite right might lead to arguments with our loved ones, and probably won’t serve us well at trivia nights. But at least our memories always vaguely resemble the truth. Right? Wrong!

The question isn’t whether our memories are false, it’s how false are our memories. Dr Julia Shaw, psychologist.

How was your balloon ride?

Far more unsettling than misremembering some aspects of a real-life event is remembering an event that never took place. Researchers now know exactly how to implant a false memory. It turns out to be an easy-to-follow recipe, particularly successful when applied to people who are ‘prone to suggestion’. What sort of false memories can you implant? Unsurprisingly, it’s easy to lead people to ‘recall’ small, made-up details about a real event they witnessed. Hey, most of us have trouble recalling the small details of our lives anyway.

But under the right circumstances, it’s possible to lead people to create wholly fake memories. Psychologists showed people doctored photos of themselves in a hot air balloon. They followed up with a guided imagery exercise and voila! Half of the study participants had memories of the completely fictitious balloon ride. Researchers also successfully got people to remember they had accidently spilled a bowl of punch on the parents of the bride at a wedding reception, despite the fact it never happened.

Participants in another study were asked to recall as many details as they could about a childhood event that was entirely made up, involving being lost at the shops. About 30 percent of the study participants later recalled being lost, some creating specific details about a kind adult who had helped them. Recollections of the fake event were less detailed than those of real events but nonetheless, these people were convinced the event had happened.

Did you commit the crime? (Are you sure?)

Can you imagine ever confessing to a crime you didn’t commit? Seems unlikely, but research has shown how easily it can happen. In one experiment, people were falsely accused of making a computer crash by pressing the wrong key during a study supposedly about reaction times. All of those accused were completely innocent. Initially, all denied the charge. But after a witness admitted to having seen it happen, many signed a confession, felt guilty and went on to form their own memories of the ‘crime’.

In another study, seventy per cent of people became convinced that as teenagers, they had committed an assault with a weapon, which led to an encounter with the police. Half of these recounted specifics of their dealings with the police. A little bit of suggestion from someone with authority goes a long way.

And of course, witnesses aren’t immune to false memories. In a series of experiments back in the 1970s, students were shown images depicting an accident between a car and pedestrian. These students were then exposed to further information about the accident: either true (the car had been at a stop sign), or misleading (the car had been at a give way sign). The results showed witnesses integrated this additional information into their memory of the event. Those who had been given the latter suggestion tended to claim they’d seen a give way sign.

Given how powerful confessions are, what does all this mean for our legal system? Plenty. In particular, that the questioning of suspects (and witnesses) must be done very, very carefully.

Will the real memory please raise its hand?

How can you tell the difference between real and false memories? With great difficulty. Because once they’ve taken hold in your brain, false memories and real memories are pretty much indistinguishable. Corroboration is your best bet so if you want to be sure something really happened, you need reliable witnesses to validate your memories for you.

A good reason to make sure you’ve got at least one friend with an excellent memory.

Links and stuff

• Video: how to implant a false memory
• TED talk: How reliable is your memory?
• The Conversation Explainer: What are false memories?
• The New Yorker: You have no idea what happened