Metacognitive Sensitivity on the Iowa Gambling Task Reveals Awareness as a Necessary Condition for Advantageous Performance

<b></b> The Somatic Marker Hypothesis (SHM) proposes that human decision-making under uncertainty is advantageously guided by affective signals before developing awareness of which courses of action are better. However, this claim has been questioned due to the limitations of the methods used to measure awareness, with alternative measures yielding conflicting results. To address this issue, we apply metacognitive sensitivity, a reliable method based on confidence ratings that outperform previous awareness measures, in an online nonclinical sample (<i>N</i> = 44) to assess awareness in the Iowa Gambling Task (IGT). Using this approach, we found that awareness and advantageous decision-making are not independent processes; an increase in metacognitive sensitivity strongly predicted an improvement in task performance in nearly all blocks of the task. A lab-based preregistered replication (<i>N</i> = 47) confirmed these findings. Interestingly, some participants demonstrated awareness without advantageous decision-making, suggesting that awareness is a necessary - but not sufficient - condition for optimal performance. Overall, this study highlights the challenges of measuring awareness in the IGT and introduces a novel alternative method that questions a key postulate of the SMH.