Consumers trust companies to tell them what to look for in a product or service: the thread count in sheets, the BTU rating for air conditioners, the cocoa butter content of premium chocolate. Companies, for their part, rarely question industry wisdom about where to direct R&D dollars to improve quality. What most influences a product’s performance, however, may not be the feature everyone assumes.

A version of this article appeared in the March 2006 issue of Harvard Business Review.