Enhanced activation of the left hemisphere promotes normative decision making

Abstract

Previous studies have reported that enhanced activation of the left cerebral hemisphere reduces risky-choice, attribute, and goal-framing effects relative to enhanced activation of the right cerebral hemisphere. The present study sought to extend these findings and show that enhanced activation of the left hemisphere also reduces violations of other normative principles, besides the invariance principle. Participants completed ratio bias (Experiment 1, N = 296) and base rate neglect problems (Experiment 2, N = 145) under normal (control) viewing or with the right or left hemisphere primarily activated by imposing a unidirectional gaze. In Experiment 1 we found that enhanced left hemispheric activation reduced the ratio bias relative to normal viewing and a group experiencing enhanced right hemispheric activation. In Experiment 2 enhanced left hemispheric activation resulted in using base rates more than normal viewing, but not significantly more than enhanced right hemispheric activation. Results suggest that hemispheric asymmetries can affect higher-order cognitive processes, such as decision-making biases. Possible theoretical accounts are discussed as well as implications for dual-process theories.

Keywords:

• Hemispheric asymmetry
• Decision making
• Focus of attention
• Processing style
• Ratio bias

This research was supported by a grant awarded to the second author from the National Science Foundation [grant number SES 0620094]. We would like to thank Sarah Pendleton, Haleigh Scott, Manuel Mendizabal, and Megan Blasczak for assisting with data collection.

This research was supported by a grant awarded to the second author from the National Science Foundation [grant number SES 0620094]. We would like to thank Sarah Pendleton, Haleigh Scott, Manuel Mendizabal, and Megan Blasczak for assisting with data collection.