Abstract. Advance of search engines has removed an end-user's constraint on search such as cost (free), operation time (fast response), language (cross-lingual), media (multimedia), and more recently, time-lag from content generation (realtime search). Consequently, we do not usually perceive strong constraint on the use of search engines. The removal of constraint is often seen as an improvement of a system's functionality which should help people improve their search performance. However, it has also been suggested that constraint can have positive effects on people's task performance. Therefore, we decided to study effects of search constraint on people's perception, behaviour, and performance. Three types of constraint were investigated: time, time + number of queries one can submit, and time + number of documents one can view. A user study with 24 participants performing background search tasks suggests that 1) query and viewing constraint can increase people's perceptional attention on query formulation and search results browsing; 2) query constraint has an effect not only on query formulation behaviour but click-through behaviour; and finally, 3) affected behaviour has medium effect on task performance. These findings warrant further studies to investigate how to leverage various forms of constraint effectively to improve human search performance.

No abstract

No abstract

No abstract

No abstract