Reality monitoring and metacognitive judgments in a false-memory paradigm

Everyday experiences are either internally generated (imagined) or externally generated (perceived). Often, the memories we form of experiences contain highly interrelated types of information. How well do we distinguish between different memory sources when the information from imagination and perception is similar? And how do metacognitive (confidence) judgments differ across different sources of experiences? To study these questions, we developed a reality monitoring task using semantically related words from the Deese-Roediger-McDermott (DRM) paradigm of false memories (Stadler et al., 1999). In an orientation phase, participants either perceived word pairs or had to voluntarily imagine the second word of a word pair. In a test phase, participants viewed words and had to judge whether the paired word was previously perceived, imagined, or new. Results revealed an interaction between memory source and judgment type on both response rates and confidence judgments: reality monitoring was better for new and perceived (compared to imagined) sources, and participants often incorrectly reported imagined experiences to be perceived. Correct perceived source judgments had the highest confidence, and individuals exhibited similar confidence between correct imagined source judgments and incorrect imagined sources reported to be perceived. Using multinomial processing trees, modeling results indicated that the observed judgments were likely due to an externalizing bias (i.e., a bias to judge the memory source as perceived). Additionally, we found that overall metacognitive ability was best in the perceived source. Finally, we used machine learning to evaluate if relationships between test stimuli and memory source conditions bias task performance. Results showed that only a classifier trained to predict participants’ responses significantly correlated with their behavior, providing evidence that orientation phase memories primarily drive performance, despite smaller influences from semantic relationships. Together, these results reveal a source-dependent effect on response rates and confidence ratings, and provide evidence that observers are surprisingly prone to externalizing biases when monitoring their own memories.