Motivated Reasoning

What is Motivated Reasoning?

A major obstacle to effective thinking is selective information processing, which is part of motivated reasoning and motivated cognition. Motivated cognition is a subconscious process which leads the mind to selectively search memory, analyze information, and reason in a way that reaches some desired conclusion.[1] What’s more, we seldom realize that our ideas or estimates are biased; instead, thanks to the illusion of objectivity, we are convinced that we’ve objectively arrived at a certain viewpoint.

Of course, there are limits to motivated reasoning. For one, there is a so-called reality constraint: people won’t reach a biased conclusion when there is clear and strong contradictory evidence. Yet, whenever contradictory evidence is not overwhelming and leaves something in the open, and people want to reach a particular conclusion, we can expect motivated reasoning to do its job. And neuroscientists have found that the reality constraint can be very weak.

Neuroscience of Motivated Reasoning

Neuroscientists have discovered that people can reach emotionally biased conclusions even when conflicting information is straightforward. What’s more, this is apparently achieved with little help from the brain’s circuits normally involved in reasoning.

During the 2004 presidential election season, Drew Westen and his colleagues used functional magnetic resonance imaging (fMRI) to look how voters’ brains react to threatening evidence about their favored candidate.[2] The researchers created fictionalized conflicting statements that the presidential candidates supposedly made. This was done to create dissonance between the subjects’ support for their candidate and that candidate’s hypocrisy. For example, the first slide about John Kerry read:

  • During the first Gulf War, John Kerry wrote to a constituent: “Thank you for contacting me to express your opposition . . . I share your concerns. I voted in favor of a resolution that would have insisted that economic sanctions be given more time to work.”

The second slide showed the contradiction:

  • Seven days later, Kerry wrote to a different constituent, “Thank you for expressing your support for the Iraqi invasion of Kuwait. From the outset of the invasion, I have strongly and unequivocally supported President Bush’s response to the crisis.”

The subjects then rated the contradiction of the candidates on a 4-point scale, 4 being the most contradictory. When subjects rated the opposition’s candidate— Democrats rating George W. Bush and Republicans rating John Kerry—they had no trouble noticing maximum contradiction. As the researchers expected, however, the subjects reached emotionally biased conclusions about their own candidate. Their own candidate’s contradiction was less obvious to them—it averaged only about 2.

The fMRI showed that the threatening information activated neural circuits responsible for distress. This unpleasant emotional state arose because of the conflict between what the data showed and what the brain wanted to see. The brain, thanks to the motivated reasoning, rapidly reached the desired conclusion. Many subjects resolved the dissonance before they saw the third slide.

Interestingly, the brain reached the desired conclusion with little help from the neural circuits normally involved in reasoning. What’s more, when it reached the desired conclusion, the brain not just turned off the negative emotion, but it also turned on neural circuits involved in positive rewards. The same positive reward circuits are also partially responsible, for example, for good feelings a drug addict gets from a fix.[3] So in a sense, the brain gave itself a fix for resolving the dissonance and reaching the biased conclusion.


[1] Ziva Kunda, The Case for Motivated Reasoning, Psychological Bulletin, 108, 480-498 (1990).

[2] Drew Westen, Pavel S. Blagov, Keith Harenski, Clint Kilts, Stephan Hamann, Neural Bases of Motivated Reasoning: An fMRI Study of Emotional Constraints on Partisan Political Judgment in the 2004 U.S. Presidential Election, Journal of Cognitive Neuroscience 18, 1947–1958 (2006).

[3] Drew Westen, The Political Brain: The Role of Emotion in Deciding the Fate of the Nation (NY: Public Affairs, 2007) p. xiv.