Even if voters have not made the conscious decision to support a candidate, their unconscious may have already made the choice for them. Using what they call an Implicit Association Test, researchers from the University of Virginia measured the responses of more than 25,000 participants to determine their implicit preference for the 2008 presidential election. (The test is still available on their website, called Project Implicit.) These unconscious biases often predicted the outcome of a voter’s decision even if that person stated he or she was undecided during the study.
Once voters arrive at a decision, it can be hard to sway them the other way, according to a study published in 2006 in the Journal of Cognitive Neuroscience. The research, led by Emory University psychology professor Drew Westen, found that when partisans listened to both positive and negative statements about their selected candidate, the area of the brain affiliated with emotional responses lit up on functional MRI scans. However, the scans showed no increased activity in the area of the brain associated with reason.