The Department of Cognitive Science cordially invites you to the public defense of the PhD thesis Interpersonal Information Integration in Judgment Revision and Collective Judgment Formation The Benefits of Distributed Access to Redundant and Complementary Visual Information in a Shared Environment by Pavel Valeryevich Voinov SUPERVISOR: Gunther Klaus Knoblich SECONDARY SUPERVISOR: Natalie Sebanz Members of the Dissertation Committee: Ágnes Melinda Kovács, Chair, CEU Chris Frith, external examiner, UCL Ilan Yaniv, external examiner, HUJ Abstract One intellectual problem where collaboration can be helpful is coming up with a quantitative judgment under uncertainty. The common consensus among scholars and researchers, though, is that people generally fail to fully realize the advantage of having plural minds. The aim of the present work is to increase our understanding of psychological and social mechanisms that allow interacting individuals to combine their uncertain knowledge into a judgment, and the causes of collective benefit and collective failure in this process. The present work addresses collective judgment as an "information integration" problem in analogy with the process of multi-sensory integration that takes place within the brain (Ernst & Bülthoff, 2004), following the original approach suggested by Bahrami et al. (2012a). It extends existing research on two lines. First, it addresses the process of inter-individual information integration under conditions implying a different degree of structural overlap in the individually available information. The second novel aspect is the focus on non-verbal modes of interaction via a shared environment. The thesis includes two empirical studies, each consisting of a series of behavioral experiments that investigate how environment-mediated interactions can support the process of inter-individual information integration under conditions of individual access to redundant and complementary information. The two studies address two conceptually different processes of inter-individual information integration: individual judgment revision and joint judgment formation. The first study investigates how indirect interactions via a shared environment can help individuals to improve their perceptual judgments by observing another's judgments. The main finding is that whether people can properly integrate observable information in the environment produced by another individual depends on their uncertainty about their own judgment. Crucially, when their own uncertainty is high, people do not discriminate between information of high and low quality in another's judgment. This leads to underperformance in the potentially most beneficial conditions - the ones where people have access to complementary information. The second study investigates how well pairs of participants can coordinate their joint judgment by means of interactions via a shared environment. It addresses the interplay between feedback on accuracy and verbal communication under conditions of simultaneous access to complementary and redundant visual information. Under conditions of access to redundant information, availability of feedback on accuracy turns out to be critical: without it interactions do not lead to an improved judgment. Verbal communication does not seem to play a crucial role, but it is helpful under conditions of access to complementary information. Furthermore, in the latter situation, a reliable collective benefit from interaction can be obtained in the absence of verbal communication, of feedback, or both. The reported studies have three major implications. First, they suggest that in a situation of collective judgment in a shared environment reliable collective benefits from interaction can be obtained without verbal communication. Second, they point to a critical role of a shared agreement on a judgment in this process. Third, they highlight the significance of the factor of structural overlap in individually held information as an important determinant of the amount of collective benefit that collaborators are likely to obtain from social interaction. . The defense will take place at room 101, V. Budapest, Október 6 street 7, 1st floor on Monday, May 29, at 10:00 a.m. With kind regards, Györgyné Finta (Réka) Department Coordinator ~~~~~~~~~~~~~~~~~~~~~~~~ Central European University Department of Cognitive Science H-1051 Budapest Oktober 6 utca 7. tel: (36-1) 887-5138 fax: (36-1) 887-5010 http://www.ceu.edu http://cognitivescience.ceu.edu