Scottish researchers used words like "barbecue" to cue memories in 30 young men and women, and then tested their ability to forget.
"For the cue word 'barbecue,' they might think of a birthday party," said study author Saima Noreen, a neuroscientist at the University of St. Andrews in Scotland. "Some of the memories were just embarrassing, like a school friend saying something unpleasant. Others were more painful, like an inappropriate touch from a family friend."
For each of 24 cue words, the study subjects were asked to recall a memory in as much detail as possible, explaining its cause, consequence and personal meaning. A week later, they were shown the same cue words in green or red.
"For the green words, we asked them to describe the memory in detail like before. But for the red words, we asked them to avoid thinking of the event," said Noreen.
That avoidance appeared to wipe out parts of the memory, as study subjects later asked to recall events linked to red-colored cue words omitted painful details.
"We found people were actually recalling significantly less about the memories they'd been told to suppress," said Noreen. "Most of time they recalled the event's cause, but the consequence and personal meaning were more susceptible to being forgotten."
The small study, published in the Journal of Experimental Psychology: Learning, Memory and Cognition, could have big implications for people plagued by painful memories.
"People with conditions like PTSD and depression have intrusive, uncontrollable negative thoughts that make them unable to move on with their lives," said Noreen, who became interested in intentional forgetting while studying depression. "Our research suggests we can actually reduce or change the accessibility of certain details."
Previous studies have hinted at the ability to deliberately forget, but this is this first to find that painful details may be particularly susceptible to the process, according to Noreen.
"You might not be able to wipe out the entire memory. But with training, you might be able to forget certain details and change your outlook on the event," said Noreen.
Forgetting is often seen as a nuisance. But it's actually essential for streamlining the process of remembering, according to Noreen. Take remembering where you parked the car on your weekly trip to the grocery store.
"You need to remember where parked today, but you also need to forget where you parked on other occasions," said Noreen. "If we didn't forget, our memories would be cluttered with irrelevant information. Part of being able to remember is having clear access to the information to we want, and that means getting rid of information we don't need."
But it's unclear whether clearing out embarrassing or painful memories can counter the effects of depression or PTSD.
"We still don't know the consequences of forgetting for mental health or wellbeing. We also don't know if these forgetting effects persist long-term," said Noreen. "A lot of research needs to be done to determine whether this has practical implications, but this is a very positive first step."