The goal of Search Assist is to provide users help with formulating their queries. Search queries either tend to be too general, i.e., the user entered too few search terms, or tend to be too specific. In the first case, even though the number of results returned is large, finding valuable information is like looking for a diamond in a haystack. In the second case, several useful results are omitted. In either case, users end up spending a lot more time struggling with reformulating their queries.
Search Assist addresses this problem. It only appears when it divines that the user needs assistance. If a pause is detected in the typing speed - a sign that the user might be pondering - Search Assist displays auto-complete suggestions as well as a set of related concepts. The set of related concepts lets a user filter the results set and further explore the different of facets of their search.
Search Assist was launched on Yahoo! Search in October 2007. A very recent study by Keynote Systems on user's search behaviour has indicated that users rated Yahoo! Search higher that any other search engine in the area of query assistance, thanks to Search Assist.
Try it: Origami on Yahoo! Search