What do you do when, say, a friendly conversation accidentally triggers a bitter memory? You probably try to put the dark thoughts out of your mind and carry on with the chat. Now a recent study in Nature Communications suggests that trying to banish that memory may cause you to forget the details of your conversation more quickly than you would have otherwise.

In the study, participants started by memorizing a number of word pairs. Researchers then showed them one word from the pair. The participants had to either retrieve or suppress the other. In between some retrieval/suppression tasks, the researchers showed the subjects unrelated pictures of objects in an unexpected setting (say, a peacock in a parking lot).

Later the team surprised the participants with a memory test in which they were shown each background setting and asked to recall the associated object. The participants were 42 percent less likely to recollect the object correctly if it had been presented between suppression tasks as opposed to recall tasks.

In another experiment described in the same paper, the researchers used functional MRI to look at participants' brain activity during retrieval and suppression. They discovered that suppression subdued activity in their hippocampus, a brain area responsible for both forming new memories and recalling old ones. This dampening may hinder the ability to register new experiences occurring at that moment. “This area of the brain doesn't have a quick on or off switch that you can simply toggle back and forth,” explains lead author Justin Hulbert, a cognitive psychologist at Bard College. “It takes some time to ramp up and down. In that process, other information that you'd like to remember later may get lost as well.”

Jesse Rissman, assistant professor in the department of psychology at the University of California, Los Angeles, says he is fascinated by the results of the study, yet he adds that it would be hard to test its real-world implications.

The findings could explain why some people report learning issues after a traumatic experience—if they often try to suppress bad memories, they might hinder their brain's ability to form new ones.