Monday, August 07, 2006

How emotions nudge rationality - brain correlates of "framing"

A very elegant report by Martino et al. from Dolan's laboratory has the title: "Frames, Biases, and Rational Decision-Making in the Human Brain"

"Human choices are remarkably susceptible to the manner in which options are presented. This so-called "framing effect" represents a striking violation of standard economic accounts of human rationality, although its underlying neurobiology is not understood. We found that the framing effect was specifically associated with amygdala activity, suggesting a key role for an emotional system in mediating decision biases. Moreover, across individuals, orbital and medial prefrontal cortex activity predicted a reduced susceptibility to the framing effect. This finding highlights the importance of incorporating emotional processes within models of human choice and suggests how the brain may modulate the effect of these biasing influences to approximate rationality."

From the brief review of this article by Miller in the same issue of Science, one example of framing:

Faced with a decision between two packages of ground beef, one labeled "80% lean," the other "20% fat," which would you choose? The meat is exactly the same, but most people would pick "80% lean." The language used to describe options often influences what people choose, a phenomenon behavioral economists call the framing effect. The Martino et al. experiments look directly at brain activity correlating with this effect.

The experiments used a novel financial decision-making task. Participants (20 university students or graduates) received a message indicating the amount of money that they would initially receive in that trial (e.g., "You receive £50"). Subjects then had to choose between a "sure" option and a "gamble" option presented in the context of two different frames. The "sure" option was formulated as either the amount of money retained from the initial starting amount (e.g., keep £20 of the £50; "Gain" frame) or as the amount of money lost from the initial amount (e.g., lose £30 of the £50; "Loss" frame). Subjects - who performed the task while inside an fMRI scanner! - were risk-averse in the Gain frame, tending to choose the sure option over the gamble option and were risk-seeking in the Loss frame, preferring the gamble option.

The amygdala (A, in the figure) was relatively more activated when subjects chose in accordance with the frame effect. When subjects made decisions that ran counter to their general behavioral tendency enhanced activity in the anterior cingulate cortex was observed (C, in the figure). This suggests an opponency between two neural systems, with ACC activation consistent with the detection of conflict between predominantly "analytic" response tendencies and a more "emotional" amygdala-based system.

Decreased susceptibility to the framing effect correlated with enhanced activity in the orbital and medial prefrontal cortex, specifically in the right orbitofrontal cortex (A, in the figure). The findings support a model in which the OMPFC evaluates and integrates emotional and cognitive information, thus underpinning more "rational" (i.e., description-invariant) behavior.

The framing bias occurs because "individuals incorporate a potentially broad range of additional emotional information into the decision process. In evolutionary terms, this mechanism may confer a strong advantage, because such contextual cues may carry useful, if not critical, information. Neglecting such information may ignore the subtle social cues that communicate elements of (possibly unconscious) knowledge that allow optimal decisions to be made in a variety of environments. However, in modern society, which contains many symbolic artifacts and where optimal decision-making often requires skills of abstraction and decontextualization, such mechanisms may render human choices irrational."

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