Involuntary memories of emotional scenes: the effects of cue discriminability and emotion over time.

Involuntary episodic memories come to mind spontaneously--that is, with no preceding retrieval attempts. Such memories are frequent in daily life, in which they are predominantly positive and often triggered by situational features matching distinctive parts of the memory. However, individuals suffering from psychological disorders, such as posttraumatic stress disorder, have stressful, repetitive, and unwanted involuntary memories about negative events in their past. These unwanted recollections are disturbing and debilitating. Although such intrusive involuntary memories are observed across a range of clinical disorders, there is no broadly agreed upon explanation of their underlying mechanisms and no successful experimental simulations of their retrieval. In a series of experiments, we experimentally manipulated the activation of involuntary episodic memories for emotional and neutral scenes and predicted their activation on the basis of manipulations carried out at encoding and retrieval. Our findings suggest that the interplay between cue discriminability at the time of retrieval and emotional arousal at the time of encoding are crucial for explaining intrusive memories following negative events. While cue distinctiveness is important directly following encoding of the scenes, emotional intensity influences retrieval after delays of 24 hr and 1 week. Voluntary remembering follows the same pattern as involuntary remembering. Our results suggest an explanatory model of intrusive involuntary memory for emotional events in clinical disorders.