The effects of encoding levels on the item and source memory of fearful and disgusting stimuli

A number of studies have shown that fear and disgust, both highly negative and arousing emotions, have better memory performance compared with neutral emotions. However, previous studies found that fear and disgust had significant differences in memory performance. Although one study has examined the effect of encoding level on item memory for fear- and disgust-related words, it remains unclear whether encoding level similarly affects item memory for fearful and disgusting images, as well as source memory for emotional images. This study examined the effects of encoding level (deep vs. shallow) and emotion type (fear, disgust and neutral) on item and source memory in three experiments.

Each experiment included three phases: encoding, distraction, and retrieval. In Experiment 1, 44 participants (24 in the deep encoding group, 20 in the shallow encoding group) were asked to complete the incidental encoding and retrieval of item and extrinsic source. In Experiment 2, 56 participants (29 in the deep encoding group, 27 in the shallow encoding group) were asked to complete the same task as in Experiment 1 in intentional encoding. In Experiment 3, 57 participants (27 in the deep encoding group, 30 in the shallow encoding group) were asked to complete the intentional encoding and retrieval of item and intrinsic source.

Our results showed that for item memory, the emotional memory advantage, especially for fearful stimuli, was observed in the shallow encoding. For source memory, no emotional memory advantage was observed in the shallow or deep encoding conditions in Experiment 1. However, in Experiments 2 and 3, fearful stimuli enhanced both frame and color source memory compared to disgusting and neutral stimuli in the shallow encoding conditions. Notably, in Experiment 3, disgusting stimuli impaired color source memory in the deep encoding conditions.

Our results suggested that fear and disgust differed in terms of item and source memory performance. However, these differences were moderated by key boundary conditions, including the level of encoding and the cognitive resource demands associated with the emotional specificity of the stimuli.