Following damage to ventromedial frontal cortices, adults with previously normal personalities develop defects in decision-making and planning that are especially revealed in an abnormal social conduct. The defect repeatedly leads to negative personal consequences. The physiopathology of this disorder is an enigma. We propose that the defect is due to an inability to activate somatic states linked to punishment and reward, that were previously experienced in association with specific social situations, and that must be reactivated in connection with anticipated outcomes of response options. During the processing that follows the perception of a social event, the experience of certain anticipated outcomes of response options would be marked by the reactivation of an appropriate somatic state. Failure to reactivate pertinent somatic markers would deprive the individual of an automatic device to signal ultimately deleterious consequences relative to responses that might nevertheless bring immediate reward (or, alternatively, signal ultimately advantageous outcomes relative to responses that might bring immediate pain). As an example, activation of somatic markers would (1) force attention to future negative consequences, permitting conscious suppression of the responses leading to them and deliberate selection of biologically advantageous responses, and (2) trigger non-conscious inhibition of response states by engagement of subcortical neurotransmitter systems linked to appetitive behaviors. An investigation of this theory in patients with frontal damage reveals that their autonomic responses to socially meaningful stimuli are indeed abnormal, suggesting that such stimuli fail to activate somatic states at the most basic level. On the contrary, elementary unconditioned stimuli (e.g. a loud noise) produce normal autonomic responses.