If you’ve seen something you’d prefer to forget, then playing Tetris might be just what you need – provided you do it within six hours. That’s the conclusion reached by a team of psychiatric researchers from Oxford University, led by Dr. Emily Holmes. In a study involving 60 test subjects, it was found that people who played the video game within six hours of viewing traumatic images had less of a tendency to experience flashbacks of those images afterward. It all has to do with the way in which the brain processes experiences.

In the first version of the Oxford experiment, all 60 volunteers were shown video footage of traumatic injuries. After half an hour, 20 of them played Tetris for 10 minutes, 20 played the text-based Pub Quiz trivia game, and 20 did nothing. Afterward, the Tetris-players had significantly fewer flashbacks to those images than the group who did nothing, while the Pub Quiz-players had the most.

In the second experiment, each group had 25 members, and the waiting time after viewing the images was extended to four hours – the results were the same. It should be noted that although the Tetris group had the fewest unwelcome flashbacks, all of the groups were equally able to remember specific details of the footage when they tried.

“Our latest findings suggest Tetris is still effective as long as it is played within a critical six-hour window after viewing a stressful film,” said Holmes. “Whilst playing Tetris can reduce flashback-type memories without wiping out the ability to make sense of the event, we have shown that not all computer games have this beneficial effect – some may even have a detrimental effect on how people deal with traumatic memories.”

According to Holmes, the effect is due to the fashion in which our minds work. Whenever we experience something, it is processed both perceptually (how it looked, sounded, tasted, etc.) and conceptually (what it meant). Usually these two channels of thought are used equally, so when we remember someone talking, for instance, we remember the sound of their voice and the meaning of what they said.

When we remember traumatic experiences, however, the perceptual channel tends to be stronger. This can result in the spontaneous resurgence of various unpleasant details, with no accompanying context to dull their impact. By looking for shapes and colors while playing Tetris, however, the perceptual channel is given something else to work on, and the traumatic memories are pushed aside. Playing something like Pub Quiz, on the other hand, occupies the conceptual channel, so it’s able to provide even less context for the unpleasant memories.

“Whist this work is still experimental, and any potential treatment is a long way off, we are beginning to understand how intrusive memories/flashbacks are formed after trauma, and how we can use science to explore new preventative treatments” said Dr. Holmes.

The research was just published in the journal PLoS ONE.