The new capabilities have been added to the personalized search service the company launched this year. The service requires users to sign up for a Google account.
By "learning" as people search, the new version is expected to deliver more relevant search results to users as they build a search history. For example, over time the technology could deliver more listings for pop music instead of classical, if a person's history showed he favored that genre.
Google, based in Mountain View, Calif., stores a person's search history on its servers, which enables a person to make use of personalized search from a browser on any computer. People can delete items from their search history, and turn off the personalized-search feature temporarily, if they don't want a web search recorded.
Privacy experts have voiced concern over Google's search-history technology, saying that it could reveal private information about the user. Such information, if stored in a server, could be made available to lawyers or government agencies with a court subpoena.
Personalized search only works with web search results, and does not support Google's other products, such as its image search.