Physiological responses reveal our political affiliations

Previous research has shown that party identifiers are more inclined to agree with policy proposals that are proposed by their own party, independent of the content of the proposal. If the same proposal is issued by a competing party, they will be inclined to respond negatively to it.

Until now, however, it has remained unclear whether this partisan bias is based on rational considerations or on more intuitive, affective reactions. Now researchers from Aarhus University in Denmark have established that only party supporters who are affectively and physiologically engaged in their party show evidence of partisan bias. Their study has been published in the journal PLOS ONE under the title "Physiological Responses and Partisan Bias."

Measuring feelings

Together with two students from Aarhus University, Professor Michael Bang Petersen has measured activity in the sympathetic nervous system -- a system responsible for the regulation of affective arousal. By attaching electrodes to the subjects' middle and index fingers, the researchers were able to identify their physiological responses.

"It's hard to measure feelings, because they often involve a range of unconscious factors. But by the use of electrodes attached to the skin, we can measure the physiological reactions of the body and thereby determine a person's affective reactions -- regardless of whether the person is aware of the reaction or not," explains Michael Bang Petersen.

During the experiment, the subjects were presented with pictures of party logos in order to identify their emotional affiliation with and sympathy towards the two major Danish parties on the left and the right, respectively: the Social Democratic Party and the Liberal Party. The subjects of the study reacted physically upon seeing the logo of the party they support.

The roots of partisan bias

The researchers were not just interested in testing whether the subjects' exhibited a physiological response to political parties. They also wanted to examine the very foundation of the partisan bias that many party supporters display.

To that end, their study included another part, where the subjects were shown eight policy proposals attributed to the Social Democratic Party and eight attributed to the Liberal Party. This included proposals concerning a wide range of policy issues; for example that income tax should be reduced and that police officers should not be allowed to wear religious symbols.

By combining the results of the two parts of the study, the researchers were able to determine a new correlation, explains Michael Bang Petersen:

"We found that subjects who had a physiological reaction during the first part of the study showed greater partisan bias in the second part of the study. For example, a great deal of the subjects who said they identified with the left-wing party tended to be sympathetic towards that party's proposals. Yet, the striking finding was that being a self-professed party identifier was not sufficient on its own. Only among those who also exhibited a strong physiological response to the logo of the party were biased towards the proposals from their own party. It was the physical reactions of the body that determined the subject's degree of bias. Our partiality seemingly stems from from instinctive emotional reactions."

Should we forget about politics and debates?

The study shows that when party supporters support a policy proposal issued by their own party, their sympathy is derived not so much from a rational analysis of policy content, but from their emotional attachment to the party in question. That being said, politics and debates have not become obsolete.

"Debates are important. Through debates, the parties signal to the voters which direction they want to take and how they plan to get there. But our results suggest that not all people are equally swayed by the person who presents the best argument. Affective reactions among sworn party identifiers will influence the degree of their agreement with proposals advocated by specific political parties -- regardless of the quality of the arguments presented," concludes Michael Bang Petersen.