The Dunning–Kruger effect (DKE) is a metacognitive phenomenon of illusory superiority in which individuals who perform poorly on a task believe they performed better than others, yet individuals who performed very well believe they under‐performed compared to others. This phenomenon has yet to be directly explored in episodic memory, nor explored for physiological correlates or reaction times. We designed a novel method to elicit the DKE via a test of item recognition while electroencephalography (EEG) was recorded. Throughout the task, participants were asked to estimate the percentile in which they performed compared to others. Results revealed participants in the bottom 25th percentile over‐estimated their percentile, while participants in the top 75th percentile under‐estimated their percentile, exhibiting the classic DKE. Reaction time measures revealed a condition‐by‐group interaction whereby over‐estimators responded faster than under‐estimators when estimating being in the top percentile and responded slower when estimating being in the bottom percentile. Between‐group EEG differences were evident between over‐estimators and under‐estimators during Dunning–Kruger responses, which revealed FN400‐like effects of familiarity supporting differences for over‐estimators, whereas “old‐new” memory event‐related potential effects revealed a late parietal component associated with recollection‐based processing for under‐estimators that was not evident for over‐estimators. Findings suggest over‐ and under‐estimators use differing cognitive processes when assessing their performance, such that under‐estimators may rely on recollection during memory while over‐estimators may draw upon excess familiarity when over‐estimating their performance. Episodic memory thus appears to play a contributory role in metacognitive judgements of illusory superiority.

The goal of this study was to investigate a relatively unstudied memory condition for paradoxical combinations of item + source memory confidence responses, which challenged the conventional views of the memory processes supporting item and source memory judgments. We studied instances in which people provided accurate source memory judgments (conventionally ascribed as representing recollection) after having first produced low-confidence item recognition hits for the same items (conventionally thought to reflect familiarity-based processing). This paradoxical combination does not fit traditional accounts of being recollection (because it had low-confidence recognition) nor accounts of familiarity (since it had accurate source memory), and event-related potentials (ERPs) were used to adjudicate which processes support these kinds of memories. ERP results were unlike the conventional ERP effects of memory, lacking both an FN400 and the parietal old-new effect (LPC), and instead exhibited a significant negative-going ERP effect occurring later in time (800-1200ms) in central-parietal sites. Behavioral measures of response times revealed a crossover interaction: low confident recognition hits were slower during recognition but faster during source memory when compared to the opposite pattern seen for instances of high confident hits. Results provide a comprehensive characterization of the individual variability of the FN400 and LPC effects of memory, while adding the behavioral and physiological characterization of a late negative-going ERP effect for accurate source memory without recollection. Conclusions indicated that episodic context could be retrieved independently from recollection, while suggesting a role for a process of context familiarity that is independent from item-familiarity.

Running title: Physiological Correlates of Dunning-Kruger EffectTotal number of words: manuscript (11, 804 words); the Abstract (250 words) Abstract.The Dunning-Kruger Effect is a metacognitive phenomenon of illusory superiority in which individuals who perform poorly on a task believe they performed well, yet individuals who performed very well believe they under-performed. This phenomenon has yet to be directly explored in episodic memory, nor explored for reaction times and physiological correlates. We designed a novel method to elicit the Dunning-Kruger Effect (DKE) via a test of item and source recognition while electroencephalography (EEG) was recorded; throughout the task, participants were asked to estimate the percentile in which they performed compared to others. Results revealed participants in the bottom 25th percentile overestimated their percentile the most, while participants in the top 75th percentile underestimated their percentile, exhibiting the classic DKE. Reaction time measures revealed a condition x group interaction whereby overestimators responded faster than under-estimators when estimating being in the top percentile and responded slower when estimating being in the bottom percentile. Between-group EEG differences were evident between over-estimators and underestimators when collapsing across all Dunning-Kruger responses, which revealed FN400-like effects of familiarity supporting differences for over-estimators from 400-600ms, whereas 'old-new' memory ERP effects revealed a late parietal component (LPC) associated with recollection-based processing for under-estimators that was not evident for over-estimators. Findings suggest over-and under-estimators use differing cognitive processes when assessing their performance, such that under-estimators rely on recollection during memory and over-estimators draw upon excess familiarity when over-estimating their performance. Episodic memory thus appears to play a contributory role in metacognitive judgments of illusory superiority in the DKE.