Adverse phenomena such as the search engine manipulation effect (SEME), where web search users change their attitude on a topic following whatever most highly-ranked search results promote, represent crucial challenges for research and industry. However, the current lack of automatic methods to comprehensively measure or increase viewpoint diversity in search results complicates the understanding and mitigation of such effects. This paper proposes a viewpoint bias metric that evaluates the divergence from a pre-defined scenario of ideal viewpoint diversity considering two essential viewpoint dimensions (i.e., stance and logic of evaluation). In a case study, we apply this metric to actual search results and find considerable viewpoint bias in search results across queries, topics, and search engines that could lead to adverse effects such as SEME. We subsequently demonstrate that viewpoint diversity in search results can be dramatically increased using existing diversification algorithms. The methods proposed in this paper can assist researchers and practitioners in evaluating and improving viewpoint diversity in search results.@en

Social choice aggregation strategies have been proposed as an explainable way to generate recommendations to groups of users. However, it is not trivial to determine the best strategy to apply for a specific group. Previous work highlighted that the performance of a group recommender system is affected by the internal diversity of the group members’ preferences. However, few of them have empirically evaluated how the specific distribution of preferences in a group determines which strategy is the most effective. Furthermore, only a few studies evaluated the impact of providing explanations for the recommendations generated with social choice aggregation strategies, by evaluating explanations and aggregation strategies in a coupled way. To fill these gaps, we present two user studies (N=399 and N=288) examining the effectiveness of social choice aggregation strategies in terms of users’ fairness perception, consensus perception, and satisfaction. We study the impact of the level of (dis-)agreement within the group on the performance of these strategies. Furthermore, we investigate the added value of textual explanations of the underlying social choice aggregation strategy used to generate the recommendation. The results of both user studies show no benefits in using social choice-based explanations for group recommendations. However, we find significant differences in the effectiveness of the social choice-based aggregation strategies in both studies. Furthermore, the specific group configuration (i.e., various scenarios of internal diversity) seems to determine the most effective aggregation strategy. These results provide useful insights on how to select the appropriate aggregation strategy for a specific group based on the level of (dis-)agreement within the group members’ preferences.@en

Advances in artificial intelligence and machine learning have led to a steep rise in the adoption of AI to augment or support human decision-making across domains. There has been an increasing body of work addressing the benefits of model interpretability and explanations to help end-users or other stakeholders decipher the inner workings of the so-called "black box AI systems". Yet, little is currently understood about the role of modalities through which explanations can be communicated (e.g., text, visualizations, or audio) to inform, augment, and shape human decision-making. In our work, we address this research gap through the lens of a credibility assessment system. Considering the deluge of information available through various channels, people constantly make decisions while considering the perceived credibility of the information they consume. However, with an increasing information overload, assessing the credibility of the information we encounter is a non-trivial task. To help users in this task, automated credibility assessment systems have been devised as decision support systems in various contexts (e.g., assessing the credibility of news or social media posts). However, for these systems to be effective in supporting users, they need to be trusted and understood. Explanations have been shown to play an essential role in informing users' reliance on decision support systems. In this paper, we investigate the influence of explanation modalities on an AI-assisted credibility assessment task. We use a between-subjects experiment (N = 375), spanning six different explanation modalities, to evaluate the role of explanation modality on the accuracy of AI-assisted decision outcomes, the perceived system trust among users, and system usability. Our results indicate that explanations play a significant role in shaping users' reliance on the decision support system and, thereby, the accuracy of decisions made. We found that users performed with higher accuracy while assessing the credibility of statements in the presence of explanations. We also found that users had a significantly harder time agreeing on statement credibility without explanations. With explanations present, text and audio explanations were more effective than graphic explanations. Additionally, we found that combining graphical with text and/or audio explanations were significantly effective. Such combinations of modalities led to a higher user performance than using graphical explanations alone.@en