“Retracted” memories influence our thoughts and behaviour just as much as real ones

False memories can seem just as real as genuine memories. It should be no surprise, then, that they influence how we think and behave. But what happens when we realise that a memory is false, and no longer believe in it — does its influence vanish? The answer, according to a new study in Memory & Cognition is: no. In fact, the work suggests a person's level of belief in a memory has surprisingly little bearing on how much it affects them.

Ryan Burnell at Waikato University, New Zealand, and colleagues ran a series of online studies to explore these "retracted" memories. A striking finding was the sheer number of people who reported them. In the first two studies, on a total of about 750 people, just over a quarter of the participants said they had a "memory" like this.

In the third study, this figure was even higher, at 45%. While some of these retracted memories were pretty hazy, others were not. For example, one participant talked about how, during some home renovations, a piece of metal had flown into his eye. Doctors told him that they could not remove the metal but his vision would not be affected. But when this man visited a doctor a few years later, he learned that there was no metal in his eye; he realised that this "memory" was completely false.

In initial studies, the team asked participants with retracted memories to report on how much they felt these memories had influenced them, such as shaping their thinking, behaviour and relationships, in either a helpful or harmful way. (A memory of being hurt in the eye might lead that person to be more cautious about DIY, for example, while a memory of doing badly in an exam might discourage someone from fresh academic studies.) The team compared these figures with participants' ratings for actual memories. They also gathered data on levels of belief in the real vs retracted memories.

In two of the team's experiments, the genuine memories came from those participants who'd reported not having any retracted memories. In two further studies, the researchers compared ratings for real and fully retracted or "doubted" memories from the same people.

There were some inconsistencies in findings across the studies. However, overall, participants reported that retracted memories had just as much of an impact on them as real memories. In fact, there was only a weak relationship between how much participants believed in a memory (or retracted memory), and how much it influenced them.

Rather, the results suggested that it was the vividness of a memory (real or false) and the extent to which someone felt able to "relive" it that determined its ongoing influence —  at least, as far as most of the helpful aspects were concerned. "Considered together, our data fit with the idea that believing a memory is 'real' is not a prerequisite for that memory to affect people's thinking and behaviour," the team concludes.

There are some limitations to the work. An important one is that the participants had to reflect on how particular memories had affected them in the past, which is a pretty big ask. Indeed, the team suggests that it might be better to experimentally implant memories and then explore their effects once participants have learned that they are actually false.

Given their new findings, it would be especially important to use only benign "memories", however - and not, for example, false memories of having committed a crime. Because, as the researchers write, "our results highlight the potential for false memories to do both lasting good and lasting harm."