During regular “blind taste tests,” in which Microsoft asks randomly-selected consumers to score the quality of results from various Internet search engines, the quality of Microsoft’s search results have so improved that people can’t tell the difference between Microsoft and Google search results, says Mr. Mehdi, senior vice president of Microsoft’s online audience business group. But when Microsoft slaps the Google brand name on the results from Microsoft’s own search engine during another portion of its tests, users invariably score them highest.