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Science 9 December 2005:
Vol. 310. no. 5754, p. 1581
DOI: 10.1126/science.310.5754.1581l
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This Week in Science

In a 2002 news briefing, U.S. Secretary of Defense Donald Rumsfeld famously distinguished between known knowns, known unknowns, and unknown unknowns. The last group remains difficult to discuss, but neuroscientists and economists have joined forces to examine the distinctions between the first two. Hsu et al. (p. 1680; see the Perspective by Rustichini) challenged subjects to choose between risky and ambiguous payoffs, where the former type of choice contains outcomes with known probabilities and the latter type features the same outcomes but with unknown probabilities. Even under conditions where the expected payoffs are equal, normal humans prefer risk over ambiguity, and brain-imaging results suggest that the amygdala and orbitofrontal cortex (OFC), which both become more active with ambiguity, modulate a third area of the brain, the striatum. Notably, patients bearing lesions in the OFC did not exhibit an aversion to ambiguity.




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