The strains of a long-forgotten song can often be the catalyst for painful, poignant or unwanted memories – but now a new study from Dartmouth and Princeton universities says these kinds of memories can be intentionally forgotten simply by changing the way we think about the context we first experienced them in.
The findings could even form the basis of mental healthcare, reducing traumatic memories in people with PTSD.
Many theories posit that context is an integral part of the way we organise and store our memories. Early research suggested that the memorisation of nonsense syllables was dramatically improved when context cues were added to the process, and "state-dependent learning" is often used as a way to improve exam scores.
In the study, published in Psychonomic Bulletin and Review, the researchers used an fMRI to track context-related memories. Participants were shown images of forests, mountains and beaches and asked to study two lists of random words, with one group asked to forget the first list and another asked to remember the first list.
"We used fMRI to track how much people were thinking of scene-related things at each moment during our experiment," said Jeremy Manning, assistant professor of psychological and brain sciences at Dartmouth and lead author of the study. "That allowed us to track, on a moment-by-moment basis, how those scene or context representations faded in and out of people's thoughts over time."
And after the first group were told to forget, the fMRI showed that they "flushed out" the context-dependent memories.
"It's like intentionally pushing thoughts of your grandmother's cooking out of your mind if you don't want to think about your grandmother at that moment," Manning says. "We were able to physically measure and quantify that process using brain data."
The study could help us understand "how we remember rather than how we forget", Manning says, and could be used to treat people experiencing flashbacks to traumatic events. "Or we might want to get old information out of our heads so we can focus on learning something new".