Here’s a spin on the depressive realism story. Shiv et al (2005) found that substance abusers and those with brain damage affecting their emotions had enhanced performance on an investment task. According to the authors of the study, the normal controls were actually distracted from making optimum decisions by their emotional involvement in the task.
‘The dark side of emotion in decision-making: When individuals with decreased emotional reactions make more advantageous decisions’ Baba Shiv, George Loewenstein and Antoine Bechara. Cognitive Brain Research, 23(1), April 2005, Pages 85-92. summary here
Can dysfunction in neural systems subserving emotion lead, under certain circumstances, to more advantageous decisions? To answer this question, we investigated how individuals with substance dependence (ISD), patients with stable focal lesions in brain regions related to emotion (lesion patients), and normal participants (normal controls) made 20 rounds of investment decisions. Like lesion patients, ISD made more advantageous decisions and ultimately earned more money from their investments than the normal controls. When normal controls either won or lost money on an investment round, they adopted a conservative strategy and became more reluctant to invest on the subsequent round, suggesting that they were more affected than lesion patients and ISD by the outcomes of decisions made in the previous rounds.