Beyond risk and ambiguity: deciding under ignorance

This study examined the neural basis of decision-making under different types of uncertainty that involve missing information: ambiguity (vague probabilities) and sample space ignorance (SSI; unknown outcomes). Functional magnetic resonance imaging (fMRI) revealed that these two different types of uncertainty recruit distinct neural substrates: ambiguity recruits the left insula whereas SSI recruits the anterior cingulate, bilateral inferior parietal cortex, and lateral orbitofrontal cortex. The finding of unique activations for different types of uncertainty may not necessarily be predicted within the reductive approach of modern theories of decision-making under uncertainty because these theories purport that humans reduce more complicated uncertain environments to subjectively formed less complicated (i.e. SSI to ambiguity). The predictions of the reductive view only held for ambiguity-averse individuals and not for ambiguity-tolerant individuals. Consequently, theories of decision-making under uncertainty should consider individual tolerance for missing information and how these individual differences modulate the neural systems engaged during decision-making