Natural Language Query vs. Keyword Search: Effects of Task Complexity on Search Performance, Participant Perceptions, and Preferences

A 2x2 mixed design experiment ( N=52) was conducted to examine the effects of search interface and task complexity on participants’ information-seeking performance and affective experience. Keyword vs. natural language search was the within-participants factor; simple vs. complex tasks was the between-participants factor. There were cross-over interactions such that complex-task participants were more successful and thought the tasks were less difficult and reported more enjoyment and confidence when they used keyword search vs. natural language queries, while the opposite was found for simple-task participants. The findings suggest that natural language search is not the panacea for all information retrieval tasks: task complexity is a critical mediator. Implications for interface design and directions for future research are discussed.