Three experiments indexed the effect of various concurrent tasks, while watching a traumatic film, on intrusive memory development. Hypotheses were based on the dual-representation theory of posttraumatic stress disorder (C. R. Brewin, T. Dalgleish, & S. Joseph, 1996). Nonclinical participants viewed a trauma film under various encoding conditions and recorded any spontaneous intrusive memories of the film over the following week in a diary. Changes in state dissociation, heart rate, and mood were also measured. As predicted, performing a visuospatial pattern tapping task at encoding significantly reduced the frequency of later intrusions, whereas a verbal distraction task increased them. Intrusive memories were largely unrelated to recall and recognition measures. Increases in dissociation and decreases in heart rate during the film were also associated with later intrusions.
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