The role of awareness, neuromodulation and metacognition in human decision making

In this thesis I have investigated the role of consciousness in human decision making and cognition and I have tried to increase our understanding about why we sometimes become aware of visual information and why sometimes not. To investigate that, I have manipulated external variables that influence our decisions, such as the visibility of visual stimuli that our decisions are based on, or visual stimuli that indicate the correctness of a previous decision (performance outcome). I have also investigated how (internal) fluctuations in the state of alertness of the brain (measured by pupil size) influence the accuracy and metacognitive insight of our decisions. In summary, using EEG measurements, we show that the brain can extract the meaning of explicit performance feedback, irrespective of the (complete) visibility of that information. However, awareness of performance outcomes seems crucial for optimal control and adaptation of our performance and it is important to learn flexibly from mistakes and adjust future choice strategies. Furthermore, increased alertness during the presentation of decision-relevant information influences both our perception of that information and the metacognitive evaluation of our decision in opposite ways. This may be due to stimulus induced noradrenaline release, a neurotransmitter amplifying the processing of external stimuli and reducing the processing of weaker internal signals. Finally, although stimuli that are hard to perceive may still affect ongoing behavior and simple decisions, these effects are not necessarily accompanied by changes in the metacognitive evaluation of decision correctness or fail to initiate control processes following difficult decisions.