The foundations of introspective access: how the relative precision of target encoding influences metacognitive performance

In metacognition research, objective performance is often matched between conditions, so that differences in type II performance (metacognition) cannot be attributed to differences in type I (task-related) performance. A recent study by Meuwese et al (2014) showed a difference in metacognitive ability when comparing metacognition in a detection and a categorization task. Interestingly, this difference only occurred in correct rejection trials, despite the fact that type I performance was matched between tasks. In the present study, we use a different manipulation to investigate the origin of these metacognitive asymmetries. We measured metacognition while matching performance in two visibility manipulations: phase-scrambling and the attentional blink. As in previous work, metacognitive asymmetries emerged: despite matched type 1 performance, metacognitive ability (measured by area under the ROC curve) for reporting stimulus absence was higher in the attentional blink condition. We performed Signal Detection Theoretic (SDT) modeling of the results, showing that differences in metacognition under equal type I performance can be explained when the variance of the signal and noise distributions are unequal. Specifically, the present study suggests that phase scrambling signal trials have a wider distribution (more variability) than attentional blink signal trials, leading to a larger area under the ROC curve for attentional blink trials where subjects reported stimulus absence. These results provide a theoretical basis for the origin of metacognitive differences on trials where subject report stimulus absence, and may also explain previous findings where the absence of evidence during detection tasks results in lower metacognitive performance when compared to categorization.