Task complexity, vertical display and user interaction in aggregated search

Aggregated search is the task of blending results from specialized search services or verticals into the Web search results. While many studies have focused on aggregated search techniques, few studies have tried to better understand how users interact with aggregated search results. This study investigates how task complexity and vertical display (the blending of vertical results into the web results) affect the use of vertical content. Twenty-nine subjects completed six search tasks of varying levels of task complexity using two aggregated search interfaces: one that blended vertical results into the web results and one that only provided indirect vertical access. Our results show that more complex tasks required significantly more interaction and that subjects completing these tasks examined more vertical results. While the amount of interaction was the same between interfaces, subjects clicked on more vertical results when these were blended into the web results. Our results also show an interaction between task complexity and vertical display; subjects clicked on more verticals when completing the more complex tasks with the interface that blended vertical results. Subjects' evaluations of the two interfaces were nearly identical, but when analyzed with respect to their interface preferences, we found a positive relationship between system evaluations and individual preferences. Subjects justified their preference using similar rationales and their comments illustrate how the display itself can influence judgments of information quality, especially in cases when the vertical results might not be relevant to the search task.