What are the underlying mechanisms for optimism bias? I have asked a question before about how does smoker's decision react to new personal health information. Link here.
 How do people estimate smoking&#39;s impact on their mortality?

Now I have a follow up question. Psychologists have termed smokers's over confidence about their chance of not being hurt by smoking as optimism bias. My question is: has there been any neuroscience, medical or psychology research about the mechanisms of optimism bias?
Optimism bias refers to a general human tendency to underestimate the likelihood of negative events, and conversely, to overestimate the likelihood of positive events, when making predictions about which events will occur to oneself in the future.

It is a cognitively interesting and widely studied phenomenon, because the human brain and human behavior are broadly believed to be highly adaptive, but optimism bias demonstrates that in many cases, we maintain beliefs in spite of the available evidence. This is a somewhat less surprising finding nowadays, since modern psychology has largely abandoned the idea of humans as rational actors. There was a time, though―a time, in Skinner's heyday, when optimism bias was considered baffling and proper paradoxical. 

Sharot (2011) suggested that optimism bias is cognitively maintained by a bias towards updating our beliefs in response to positive prospective information than to negative prospective information. She attributed this to decreased encoding of negative-update information in the right inferior frontal gyrus. In another paper, Sharot, Riccardi, Raio and Phelps (2007) had reported this decreased encoding may be mediated by activity in the rostral anterior cingulate cortex (rACC) and amygdala:


  Here we report that [optimism bias] was related specifically to enhanced activation in the amygdala and in the rostral anterior cingulate cortex when imagining positive future events relative to negative ones, suggesting a key role for areas involved in monitoring emotional salience in mediating the optimism bias.


In other words, the amygdala appears to evaluate the emotion valence of the information, evoking a regulatory response in the rACC, which is implemented as an inhibited update to negative-update evidence, or optimism bias, by the right inferior frontal gyrus.

References


Sharot, T. (2011). The optimism bias. Current Biology, 21(23), R941-R945.
Sharot, T., Riccardi, A. M., Raio, C. M., &amp; Phelps, E. A. (2007). Neural mechanisms mediating optimism bias. Nature, 450(7166), 102-105.