Investigating Cognitive Effects in Session-level Search User Satisfaction

User satisfaction is an important variable in Web search evaluation studies and has received more and more attention in recent years. Many studies regard user satisfaction as the ground truth for designing better evaluation metrics. However, most of the existing studies focus on designing Cranfield-like evaluation metrics to reflect user satisfaction at query-level. As information need becomes more and more complex, users often need multiple queries and multi-round search interactions to complete a search task (e.g. exploratory search). In those cases, how to characterize the user's satisfaction during a search session still remains to be investigated. In this paper, we collect a dataset through a laboratory study in which users need to complete some complex search tasks. With the help of hierarchical linear models (HLM), we try to reveal how user's query-level and session-level satisfaction are affected by different cognitive effects. A number of interesting findings are made. At query level, we found that although the relevance of top-ranked documents have important impacts (primacy effect), the average/maximum of perceived usefulness of clicked documents is a much better sign of user satisfaction. At session level, perceived satisfaction for a particular query is also affected by the other queries in the same session (anchor effect or expectation effect). We also found that session-level satisfaction correlates mostly with the last query in the session (recency effect). The findings will help us design better session-level user behavior models and corresponding evaluation metrics.