Do positive and negative somatic markers precede good and bad choices before explicit knowledge is available?

Recent evidence suggests that somatic markers mediate decision- making processes by signaling potential rewards and punishments before conscious knowledge is available (Bechara et al., 2000, Cerebral Cortex, 295–307). The present study investigated wheth- er anticipatory electrodermal responses to good and bad choices modulate choosing advantageously in a gambling task before ex- plicit knowledge about the rules of the task is available. Forty-six undergraduates performed a computerized version of the gam- bling task while participants’ preferences toward the four decks of cards, their knowledge of the rules of the task (yes/no) and wheth- er they could describe them as well as changes in electrodermal activity were measured. Participants were a-posteriori divided in two groups based on their knowledge of the rules by trial 100. Results showed that by trial 50, participants in the “knowledge group” had made more advantageous choices and they had devel- oped clear preferences toward the advantageous decks. Anticipa- tory EDRs before making a choice varied significantly between the two groups throughout the task. More specifically, between rials 21 and 41, participants in the “knowledge group” showed larger anticipatory EDRs before choosing disadvantageously as well as before choosing advantageously. The present results sup- port the notion that positive and negative somatic markers modu- late decision making by helping developing preferences before explicit knowledge is available.