BBC looks into our brains, watching scans that show how one memory can literally replace a different, but similar one:
“People are used to thinking of forgetting as something passive,” said lead author Dr Maria Wimber from the University of Birmingham.
“Our research reveals that people are more engaged than they realise in shaping what they remember of their lives.”
“It’s not that we’re pushing something out of our head every time we’re putting something new in.
“The brain seems to think that the things we use frequently are the things that are really valuable to us. So it’s trying to keep things clear – to make sure that we can access those important things really easily, and push out of the way those things that are competing or interfering.”
The idea that frequently recalling something can cause us to forget closely related memories is not new; Dr Wimber explained that it had “been around since the 1990s”.
But never before had scientists managed to confirm that this was the result of an active suppression of the interfering memory, rather than just a passive deterioration.
This might involve looking at a picture of Marilyn Monroe, or Albert Einstein, many times over.
“We show people visual pictures of these memories over and over again – and we can sample the prototypical brain response to those pictures,” Dr Wimber explained.
This allowed the researchers to discover what was distinctive about the “Monroe” pattern compared to the “Einstein” one.
Then, by triggering them both with the same, unrelated word (eg “sand”) but only asking for one to be remembered, they were able to watch, say, the Monroe trace persist while Einstein withered and faded.
The study was originally published in Nature Neuroscience.