Following a study showing that playing Tetris after traumatic events could reduce memory flashbacks in healthy volunteers, two experiments have found playing Tetris after viewing traumatic images significantly reduced flashbacks while playing Pub Quiz Machine 2008 (a word-based quiz game) increased the frequency of flashbacks. In the experiments, volunteers were shown a film that included traumatic images of injury.
In the first experiment, after waiting for 30 minutes, 20 volunteers played Tetris for 10 minutes, 20 played Pub Quiz for 10 minutes and 20 did nothing. In the second experiment, this wait was extended to four hours, with 25 volunteers in each group.
In both experiments, those who played Tetris had significantly fewer flashbacks that the other two groups, and all groups were equally able to recall specific details of the film. Flashbacks were monitored for a week.
It is thought that with traumatic information, perceptual information is emphasized over conceptual information, meaning we are less likely to remember the experience of being in a high-speed road traffic collision as a coherent story, and more likely to remember it by the flash of headlights and noise of a crash. This perceptual information then pops up repeatedly in the victim's mind in the form of flashbacks to the trauma causing great emotional distress, as little conceptual meaning has been attached to them. If you experience other events that involve similar information, during the time window in which the traumatic memories are being processed, that information will interfere with that processing.
Thus, the spatial tasks of Tetris (which involves moving and rotating shapes) are thought to compete with the images of trauma, while answering general knowledge questions in the Pub Quiz game competes with remembering the contextual meaning of the trauma, so the visual memories are reinforced and the flashbacks are increased.
 . Can Playing the Computer Game “Tetris” Reduce the Build-Up of Flashbacks for Trauma? A Proposal from Cognitive Science. PLoS ONE [Internet]. 2009 ;4(1):e4153 - e4153. Available from: http://dx.doi.org/10.1371/journal.pone.0004153