Hemispheric mechanisms and sequential modality effects in risky choices

Hemispheric asymmetry and modality were examined as a function of risky choice behavior in human decision making. Participants were asked to evaluate two alternative plans in terms of their estimated outcomes and then to make their choice between the two plans. The two options differed in their riskiness, one a "sure thing" and one a gamble of the same expected values for scenarios involving both money and lives.;A modified dichotic listening technique was used to present the plans while an unrelated message was presented simultaneously to the opposed ear. The competition for pathways between the messages allowed selected messages to be registered hemispherically. Participants' minimum requirement (MR) for making their decision was also measured. Under positive framing, a risk-averse preference (choice for the sure thing) is typically dominant; with negative framing, a risk-seeking (choice for the gamble) is dominant, a cognitive phenomenon which is known as framing effect. Risk preference patterns for left ear-right hemisphere (LE-RH) participants were consistent with the prediction that they would be more sensitive to the emotional cues in choice problems. Specifically, framing effects were found for LE-RH participants; however, no significant framing effects were found for right ear-left hemisphere (RE-LH) participants.;Significant effects for the modality of presentation were found; under dichotic/auditory conditions, participants used simpler risk strategies. Changes in risk preference patterns under visual conditions were more variable than were found in the dichotic condition. Consistent with previous findings, risk preference patterns showed a group size, social-context specific pattern. In part, framing effects occurred when people dealt with large numbers of lives in anonymous contexts.;Finally, MR results supported a mean-variance model of human risky decision behavior (Wang, 1996c). MR was higher (visual conditions only) in the kinship context than in anonymous stranger contexts. MR was generally higher for participants under negative framing, lower when switching to positive framing, and higher under kinship conditions. This study suggests that risk-sensitive and social-context dependent mechanisms may be lateralized with the right hemisphere being specialized for the processing of emotional cues. The study lends further support for a mean-variance model of human decision behavior.