As technology has opened new windows into the brain, it has clarified what happens there when people make decisions about money. This clarity has produced a new science called neuroeconomics, which addresses diverse questions, such as why people save, buy stocks, steal, and overspend. The many different methods used in neuroeconomics have, however, often yielded unclear findings about the quality of these decisions, primarily because the field has lacked both guidelines for categorizing the different aspects of quality, and guidelines for selecting methods to study these aspects.

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