nep-exp New Economics Papers
on Experimental Economics
Issue of 2009‒06‒10
two papers chosen by
Daniel Houser
George Mason University

  1. Two's Company, Three's a Group: The impact of group identity and group size on in-group favouritism By Donna Harris; Benedikt Herrmann; Andreas Kontoleon
  2. An Empirical Comparison of Dissimilarity Measures for Recommender Systems By Kagie, M.; Wezel, M.C. van; Groenen, P.J.F.

  1. By: Donna Harris (Environmental Economy and Policy Research Group, Department of Land Economy, University of Cambridge, 19 Silver Street, Cambridge, UK, CB3 9EP.); Benedikt Herrmann (CeDEx, School of Economics, University of Nottingham, UK, NG7 2RD.); Andreas Kontoleon (Department of Land Economy, University of Cambridge)
    Abstract: In this study, we use an allocation game to study the effects of group identity and group size on in-group favouritism when the person's own payoff is not affected by her decision. We first show that in a triadic setting when the subjects are asked to allocate a fixed amount of resource between two other anonymous individuals, the majority of the subjects choose to allocate equal amounts to both the in-group and the out-group members. Contrary to previous studies, when group identity is induced artificially by simply telling the subjects that they belong to the same `group', it does not appear to significantly increase the amount allocated to the in-group member relative to the out-group member in a triadic setting. However, once the number of the in-group recipients is increased from one to three, the same artificial group identity triggers a sharp increase in in-group favouritism. Our results suggest that in order for favouritism to be clearly observed, not only that group identity has to be present, but also the group needs to consist of more than two members.
    Keywords: Favouritism, Group Identity, Group Behaviour, Group Size, Design of Laboratory Experiment
    Date: 2009
  2. By: Kagie, M.; Wezel, M.C. van; Groenen, P.J.F. (Erasmus Research Institute of Management (ERIM), RSM Erasmus University)
    Abstract: Many content-based recommendation approaches are based on a dissimilarity measure based on the product attributes. In this paper, we evaluate four dissimilarity measures for product recommendation using an online survey. In this survey, we asked users to specify which products they considered to be relevant recommendations given a reference product. We used microwave ovens as product category. Based on these responses, we create a relative relevance matrix we use to evaluate the dissimilarity measures with. Also, we use this matrix to estimate weights to be used in the dissimilarity measures. In this way, we evaluate four dissimilarity measures: the Euclidean Distance, the Hamming Distance, the Heterogeneous Euclidean-Overlap Metric, and the Adapted Gower Coefficient. The evaluation shows that these weights improve recommendation performance. Furthermore, the experiments indicate that when recommending a single product, the Heterogeneous Euclidean-Overlap Metric should be used and when recommending more than one product the Adapted Gower Coefficient is the best alternative. Finally, we compare these dissimilarity measures with a collaborative method and show that this method performs worse than the dissimilarity based approaches.
    Keywords: dissimilarity;case-based recommendation;evaluation;weight estimation
    Date: 2009–05–07

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