This should interest the commentariat.
A new brain imaging study published this month in Cell Biology finds that self-identified liberals and conservatives have measurably different gray matter volume in certain brain structures. This tracks with a few recent studies linking political orientation with cognitive process patterns, activation potentials, facial recognition responses, and other measures. It adds to a small but growing body of studies linking physical brain typology, cognitive function and political outlook.
Our findings extend previous observations that political attitudes reflect differences in self-regulatory conflict monitoring  and recognition of emotional faces  by showing that such attitudes are reflected in human brain structure. Although our data do not determine whether these regions play a causal role in the formation of political attitudes, they converge with previous work [ and ] to suggest a possible link between brain structure and psychological mechanisms that mediate political attitudes.
In liberal brains, according to neuroimaging, greater liberalism is associated with increased gray matter volume in the anterior cingulate cortex, a part of the brain associated with conflict (i.e. contradiction) detection, detection of error and similar problem-finding activities.
It seems help detect errors involved in habitual tasks or repetitive stimuli. An adjacent area of the ACC appears to act as a link between higher cognitive forebrain activity and the emotional limbic system (empathy, etc.). From the pathology section of the wiki:
Studying the effects of damage to the ACC provides insights into the type of functions it serves in the intact brain. Behavior that is associated with lesions in the ACC includes: inability to detect errors, severe difficulty with resolving stimulus conflict in a Stroop task, emotional instability, inattention, and akinetic mutism. There is evidence that damage to ACC is present in patients with schizophrenia, where studies have shown patients have difficulty in dealing with conflicting spatial locations in a Stroop-like task and having abnormal ERNs. Participants with ADHD were found to have reduced activation in the dorsal area of the ACC when performing the Stroop task. Together these findings corroborate results from imaging and electrical studies about the variety of functions attributed to the ACC.
There is evidence that this area may have a role in obsessive–compulsive disorder due to the fact that what appears to be an unnaturally low level of glutamate activity in this region has been observed in patients with the disorder, in strange contrast to many other brain regions that are thought to have excessive glutamate activity in OCD.
In conservative brains, greater conservatism is associated with increased gray matter in the right amygdala.
Research shows that the amygdalae perform a primary role in processing memory and emotional response, particularly with the process of "emotional learning," as well as long-term memory formation. The amygdalae are commonly associated with fear and fear-conditioning, although their actual functions are quite a bit more complex and are better described as centers for emotionally-charged memory. Emotional intelligence and social network size are positively correlated (i.e. people with big amygdalae have more friends and are more "in touch" with their feelings).
Artistic types have higher than usual readings of amygdala activity...in fact given the connection from powerful emotion to memory, you could think of the two amygdalae as the 'Proust regions' of the brain.
As far as fear goes, as a component of the limbic system the amygdalae are directly involved in the physiology of fear responses, as well as fear-based (i.e. behaviorist) conditioning.
The central nuclei are involved in the genesis of many fear responses, including freezing (immobility), tachycardia (rapid heartbeat), increased respiration, and stress-hormone release. Damage to the amygdalae impairs both the acquisition and expression of Pavlovian fear conditioning, a form of classical conditioning of emotional responses.
Notable pathologies involved in over-developed amygdalae include Borderline Personality Disorder (extreme black-white thinking, paranoia, "overreacting," emotional instability), schizophrenia, the phenomenon known as "amygdala hijack," essentially, overreaction to a perceived threat. Emotion-driven decision making can be a bad thing.
By the way, one of the authors listed on the study, Colin Firth, isn't just some lab geek who has to endure endless hazing because he shares a name with noted and Oscar-winning actor Colin Firth. He *is* noted and Oscar-winning actor Colin Firth. I hope this doesn't detract from the report's credibility.