DECIDING ADVANTAGEOUSLY BEFORE KNOWING THE ADVANTAGEOUS STRATEGY

Deciding advantageously in a complex situation is thought to require o vert reasoning on declarative knowledge, namely, on facts pertaining t o premises, options for action, and outcomes of actions that embody th e pertinent previous experience. An alternative possibility was invest igated: that overt reasoning is preceded by a nonconscious biasing ste p that uses neural systems other than those that support declarative k nowledge. Normal participants and patients with prefrontal damage and decision-making defects performed a gambling task in which behavioral, psychophysiological, and self-account measures were obtained in paral lel. Normals began to choose advantageously before they realized which strategy worked best, whereas prefrontal patients continued to choose disadvantageously even after they knew the correct strategy. Moreover , normals began to generate anticipatory skin conductance responses (S CRs) whenever they pondered a choice that turned out to be risky, befo re they knew explicitly that it was a risky choice, whereas patients n ever developed anticipatory SCRs, although some eventually realized wh ich choices were risky. The results suggest that, in normal individual s, nonconscious biases guide behavior before conscious knowledge does. Without the help of such biases, overt knowledge may be insufficient to ensure advantageous behavior.