Does enhanced memory of disgust vs. fear images extend to involuntary memory?

People remember disgusting stimuli better than fearful stimuli, but do disgust's memory-enhancing effects extend to involuntary memory? This question is important because disgust reactions occur following trauma, and trauma-related involuntary memories are a hallmark of Posttraumatic Stress Disorder (PTSD) symptoms. In two experiments, we presented participants (n = 88 Experiment 1; n = 106 Experiment 2) with disgust, fear, and neutral images during an attention-monitoring task. Participants then completed an undemanding vigilance task, responding any time an image involuntarily came to mind. We measured the frequency and characteristics of these involuntary memories (e.g. emotional intensity) immediately after encoding and over a 24-hour delay (Experiment 2 only). Our main findings were mixed: participants experienced similarly frequent (Experiment 2) - or more (Experiment 1) - disgust as fear involuntary memories. Therefore, when controlling for memory-enhancing confounds (e.g. distinctiveness), in-laboratory disgust memory enhancement does not extend to involuntary memory. Disgust memories were more emotionally intense than fear memories over the 24-hour delay- but not immediately after encoding - suggesting disgust elicits additional consolidation processes to fear. Participants paid more attention towards the disgust images, but the attention did not account for the memory of disgust. In sum, disgust and fear have both similar and distinct cognitive effects.