Title: "Group Counterfactuals for Bias Detection, Mitigation and Subgroup Identification"

Speaker: Panagiotis Tsaparas (University of Ioannina, Greece and Lead P.I. in Archimedes Unit, RC Athena)

Abstract: Counterfactual explanations can be used as a means to explain a models decision process and to provide recommendations to users on how to improve their current status. The difficulty to apply these counterfactual recommendations from the users perspective, also known as burden, may be used to assess the models algorithmic fairness and to provide fair recommendations among different sensitive feature groups. We propose a novel model-agnostic, mathematical programming-based, group counterfactual algorithm that can: (1) detect biases via group counterfactual burden, (2) produce fair recommendations among sensitive groups and (3) identify relevant subgroups of instances through shared counterfactuals. We analyze these capabilities from the perspective of recourse fairness, and empirically compare our proposed method with the state-of-the-art algorithms for group counterfactual generation in order to assess the bias identification and the capabilities in group counterfactual effectiveness and burden minimization.

Short Bio: Panayiotis Tsaparas is Associate Professor at the Department of Computer Science and Engineering at University of Ioannina. He received his Ph.D. from University of Toronto in 2003. Before joining University of Ioannina, he worked as a post-doctoral fellow at University of Rome, “La Sapienza” (2004) and at University of Helsinki (2004-2006), and as a researcher at Microsoft Research (2006-2011). His research interests include Data Mining & Machine Learning, Social Network Analysis, and Algorithmic Fairness. He is a Senior ACM member., and he has served several times as a PC and Senior PC member for premier Data Mining and Data Bases conferences such as KDD, WWW, WSDM, VLDB, ICDE, and as reviewer for journals such as TKDE, TWEB, CACM, TODS, KAIS, DMKD. He is currently PC co-Chair for WSDM 2023, and an associate editor for the TKDE and OSNM journals. He has published 71 papers in peer-reviewed conferences and journals, and has filed for 12 patents, 8 of which have been awarded.