Manipulation of working memory contents selectively impairs metacognitive sensitivity in a concurrent visual discrimination task

What are the cognitive mechanisms underlying perceptual metacognition? Prior research indicates that prefrontal cortex (PFC) contributes to metacognitive performance, suggesting that metacognitive judgments are supported by high-level cognitive operations. We explored this hypothesis by investigating metacognitive performance for a visual discrimination task in the context of a concurrent working memory (WM) task. We found that, overall, high WM load caused a nonspecific decrease in visual discrimination performance as well as metacognitive performance. However, active manipulation of WM contents caused a selective decrease in metacognitive performance without impairing visual discrimination performance. These behavioral findings are consistent with previous neuroscience findings that high-level PFC is engaged by and necessary for (i) visual metacognition, and (ii) active manipulation of WM contents, but not mere maintenance. The selective interference of WM manipulation on metacognition suggests that these seemingly disparate cognitive functions in fact recruit common cognitive mechanisms. The common cognitive underpinning of these tasks may consist in (i) higher-order re-representation of lower-level sensory information, and/or (ii) application of decision rules in order to transform representations in PFC into definite cognitive/motor responses.