Neurological evidence for contrast between emotional and rational decision-making

Ever since Plato philosophers and then scientists have talked about the contrasting roles of emotions and reason in our decision making. Usually, emotions get the short shrift, epitomized by the Star Trek characters of Spock and Data, who are so efficient and cool precisely because they are all rationality and no emotion. Then again, David Hume recognized the fundamental motivational role of emotions, and famously said that “Reason is, and ought only to be the slave of the passions” (Dr. McCoy couldn't have said it better himself!).

A recent paper in Science magazine (4 August 2006, pp. 684-687) by Benedetto De Martino and collaborators has made a major contribution to the scientific investigation of how exactly emotions and reason interplay in our daily lives. First of all, they demonstrated that subjects were making different decisions according to how a particular choice was presented, what is known as the “framing effect.” It turns out that given exactly the same choices, people tend to take more risks if the problem is framed in a negative sense (“you are going to lose $30 out of $50”) than in a positive one (“you are going to win $20 out of $50”). Using a functional MRI scan of the brain, the investigators found that the framing effect was correlated with the activity of the amygdalas, structures well-known to be associated with emotional reactions.

De Martino et al. then investigated what was happening in the brain when subjects were making decisions that were contrary to their general tendency, i.e., when they were using their rational analysis to override their emotional inclinations. In this case, the anterior cingulate cortex was activated, indicating a role of this structure in countering the influence of the amygdalas. The scientists then noticed that there was variation among subjects for their sensitivity to the framing effect, and traced these differences to the degree of activity of a third area of the brain, the orbital and medial prefrontal cortex: the higher the activation of the cortex, the more the subjects behaved rationally and the least they were susceptible to the emotionally-driven framing effect. Previous research had shown that lesions in the orbital and medial prefrontal cortex lead to impairments in decision-making ability, and in particular to impulsive decisions with little regard for long-term consequences.

I'm not sure what this says about the murky concept of “free will,” but it certainly suggests that our brains have a complex and interacting circuitry that allows us to make decisions based on a balanced combination of emotions, rational thinking, and external information. This circuitry can be put off balance by a variety of factors, including presumably emotional stress, or low-quality information available to the brain. Lest you scoff at this as being only of academic interest, think of how crucial the question of “framing” is in political debate, and how the current Republican administration both plays on highly emotional issues (fear-mongering for the “war on terror,” homophobia for gay marriages) and provides the public with distorted information (weapons of mass destruction, the alleged inability of gay couples to raise children). Science is only beginning to catch up with political demagoguery.