1. A computer-implemented method comprising: a) providing, by a computer system having at least one computer in a network, responsive to a received search query, a document with a plurality of search results, wherein the search query has at least two different semantic interpretations corresponding to two different user information needs, the plurality of search results including i) a first search result associated with a first document having content concerning a first topic related to a first semantic interpretation of the search query, and ii) a second search result associated with a second document having content concerning a second topic related to a second semantic interpretation of the search query; b) determining, by the computer system, which of the first and second semantic interpretations of the search query a user is most interested in based on behavior of the user with respect to one of the first and second search results; c) selecting, by the computer system, one of a first set of one or more ads relevant to the first topic or a second set of one or more ads relevant to the second topic using, at least, the determination of user topic interest, wherein the first set of one or more ads is different from the second set of one or more ads; and d) serving, by the computer system, in association with the document, the selected one of the first or second set of one or more ads.
3. The computer-implemented method of claim 1 wherein the act of determining which of the first topic and the second topic a user is most interested in further includes monitoring at least one of (a) cursor positioning with respect to at least one of the first and second search results, (b) cursor dwell time with respect to at least one of the first and second search results, (c) user eye direction with respect to at least one of the first and second search results, (d) user facial expressions with respect to at least one of the first and second search results, (e) user expressions with respect to at least one of the first and second search results, or (f) express user topic interest input with respect to at least one of the first and second search results.