I still think a large portion of studies like this are representative of (probably unintentional) sampling bias ...
A large portion of people’s political orientation is determined by their values and beliefs they generated over decades of their life experiences and social interactions. Often, simply by moving from one region in a country to another and having a completely different series of life experiences will drastically impact a person’s political views; as can be witnessed in Canada, as hundreds of thousands of people have moved from liberal regions of the country to conservative Alberta and adopted the conservative views of the region after a couple of years. I find it impossible to believe that this political conversion is the result of a drastic change in brain structure.
Why this is important is that two people who share political ideals in two different regions may do so based on two drastically different life experiences and social interactions. Effectively, a conservative in a conservative region probably bases their political views on what they see as the successes of conservative ideology, while a conservative in a more progressive region may base their political views on what they see as the failure of progressive ideology; and you could (probably) say something similar about more progressive voters. Unless you do a broad study that controls for countless socioeconomic factors, it is likely that your results are being heavily skewed.
