In conjunction with the 7th ACM Conference on Recommender Systems October Hong Kong China Preface

Users interact with recommender systems to obtain useful information about products or services that may be of interest for them. But, while users are interacting with a recommender system to fulfill a primary task, which is usually the selection of one or more items, they are facing several other decision problems. For instance, they may be requested to select specific feature values (e.g., camera’s size, zoom) as criteria for a search, or they could have to identify features to be used in a critiquing based recommendation session, or they may need to select a repair proposal for inconsistent user preferences when interacting with a recommender. In all these scenarios, and in many others, users of recommender systems are facing decision tasks. The complexity of decision tasks, limited cognitive resources of users, and the tendency to keep the overall decision effort as low as possible is modeled by theories that conjecture “bounded rationality”, i.e., users are exploiting decision heuristics rather than trying to take an optimal. Furthermore, preferences of users will likely change throughout a recommendation session, i.e., preferences are constructed in a specific decision context and users may not fully know their preferences beforehand. Within the scope of a decision process, preferences are strongly influenced by the goals of the customer, existing cognitive constraints, and the personal experience of the customer. Due to the fact that users do not have stable preferences, the interaction mechanisms provided by a recommender system and the information shown to a user can have an enormous impact on the outcome of a decision process.

Theories from decision psychology and cognitive psychology have already elaborated a number of methodological tools for explaining and predicting the user behavior in these scenarios. The major goal of this workshop is to establish a platform for industry and academia to present and discuss new ideas and research results that are related to the topic of human decision making in recommender systems. The workshop consists of a mix of six presentations of papers in which results of ongoing research as reported in these proceedings are presented and two invited talks: Bart Knijnenburg presenting “Simplifying privacy decisions: towards interactive and adaptive solutions” and and Jill Freyne and Shlomo Berkovsky presenting: “Food Recommendations: Biases that Underpin Ratings”. The workshop is closed by a final discussion session.

Li Chen, Marco de Gemmis, Alexander Felfernig, Pasquale Lops, Francesco Ricci, Giovanni Semeraro and Martijn Willemsen

September 2013

 Workshop Committee Workshop Co-Chairs Li Chen, Hong Kong Baptist University Marco de Gemmis, University of Bari Aldo Moro, Italy Alexander Felfernig, Graz University of Technology, Austria Pasquale Lops, University of Bari Aldo Moro, Italy Francesco Ricci, University of Bozen‐Bolzano, Italy Giovanni Semeraro, University of Bari Aldo Moro, Italy Martijn Willemsen, Eindhoven University of Technology, Netherlands Organization Gerald Ninaus, Graz University of Technology Program Committee David Amid, IBM Haifa Research Center Shlomo Berkovsky, NICTA Robin Burke, DePaul University Li Chen, Hong Kong Baptist University Marco De Gemmis, Dipartimento di Informatica – University of Bari Alexander Felfernig, Graz University of Technology Gerhard Friedrich, Alpen-Adria-Universitaet Klagenfurt Sergiu Gordea, AIT Anthony Jameson, DFKI Dietmar Jannach, TU Dortmund Bart Knijnenburg, University of California, Irvine Gerhard Leitner, Alpen-Adria-Universitaet Klagenfurt Pasquale Lops, University of Bari Gerald Ninaus, Graz University of Technology Florian Reinfrank, Graz University of Technology Francesco Ricci, Free University of Bozen-Bolzano Giovanni Semeraro, Dipartimento di Informatica – University of Bari Ofer Shir, IBM Research Erich Teppan, Alpen-Adria-Universitaet Klagenfurt Martijn Willemsen, Eindhoven University of Technology Markus Zanker, Alpen-Adria-Universitaet Klagenfurt Accepted papers

Efficiency Improvement of Neutrality-Enhanced Recommendation Toshihiro Kamishima, Shotaro Akaho, Hideki Asoh and Jun Sakuma Towards User Profile-based Interfaces for Exploration of Large Collections of Items Claudia Becerra, Sergio Jimenez and Alexander Gelbukh Selecting Gestural User Interaction Patterns for Recommender Applications on Smartphones Wolfgang Wörndl, Jan Weicker and Béatrice Lamche 17 The Role of Emotions in Context-aware Recommendation Yong Zheng, Bamshad Mobasher and Robin Burke Managing Irrelevant Contextual Categories in a Movie Recommender System Ante Odić, Marko Tkalcic and Andrej Kosir An Improved Data Aggregation Strategy for Group Recommendations Toon De Pessemier, Simon Dooms and Luc Martens

 Invited presentations

Simplifying privacy decisions: towards interactive and adaptive solutions Bart Knijnenburg Food Recommendations: Biases that Underpin Ratings Jill Freyne and Shlomo Berkovsky 1 9 21 29 36 40 42

Copyright © 2013 for the individual papers by the papers' authors. Copying permitted for

private and academic purposes. This volume is published and copyrighted by its editors.