The effect of dissociation at encoding on intrusive memories for a stressful film

The occurrence of memory intrusions after a trauma has been linked to peri-traumatic dissociation. In this study, we attempted to induce dissociation experimentally and investigate the impact on intrusive memories. A total of 39 undergraduates were randomly assigned to watch a stressful film under standard conditions or under a dual-task condition in which they simultaneously performed a tapping task. They rated their distress post-film and again after 2 weeks, and kept a diary of intrusive memories. Contrary to prediction, there were no differences in levels of distress or explicit memory between the two conditions, and the dual-task condition was followed by significantly fewer memory intrusions. Dual-task conditions may not provide a good analogue to naturally occurring dissociation. The possible preventive effects of the tapping task are discussed in terms of the dual-representation theory of post-traumatic stress disorder.