Dalla Razionalità Individuale alla Razionalità di Gruppo.

The aim of the thesis was the analysis of consequences from a cognitive, psyho- sociological and economic point of view of considering an individual facing decisions within a group and not isolated. We have analyzed consequences on cognitive processes of an individual considered within a group. From the economical point of view we have underlined that beyond the private utility of an object there is also a social value of it and individuals take in consideration both, we have analyzed how a rational individual behaves within a group and not isolated. There are internal dynamics of the group, involving entirely each member, to such an extent to create a strong and almost all-encompassing In-Group Bias. Precisely, the first thing determined by group identity and group membership is the distinction between ingroup and outgroup members, and this will be the two most important categories. We have outlined the four determinants of In-Group Bias: cooperation, competition, common fate and similarity. After, we moved the analysis on the cognitive level, we tried to understand, from a cognitive point of view, what is a group for an agent, what is the role that a group can have for an agent. Thus as first thing, we introduced the concept of social categorization; how social categorization, contextualized by intergroup relations, in- fluences social cognition processes and structures within groups. We focused our attention at perception processes on three different levels; perception of individuals, of groups and of an individual as member of a group. We have seen by comparing the principles of perception for individuals and groups which are the differences and the conditions to resolve these differences. Secondly we studied the potential induc- tive power that a group might have for the perceiver, what are the conditions in which the knowledge of group membership of an individual may be relevant for the perceiver. The principal factor, influencing the inductive power, is the entativity of the group, the degree of unity of the group; the higher is the degree of entativity and higher is the probability that group members will be evaluated in terms of the expectancies associated with the group. The third analysis is from the point of view of economic theory: two are the main models, so far created, to study an agent within a social group, the direct and the indirect or instrumental method. The direct method considers economic agents interested in the opinions of others in purely personal terms, agents are interested in the opinion that peers have of their actions only because it concerns his own person with no interest for the family, or the children or in general for the offspring. The second method, indirect or instrumental, models the behavior of people interested in the opinions of others not for themselves but because those views indirectly affect goods and services which they and their children (or descendants) will enjoy. So this second way of modeling seeks to understand and grasp distortions from the standard rational behavior of an individual, due to the consideration of those factors that indirectly affect utility. The third chapter is a direct consequence of the observations made in previous chapters. We have tried to translate in economic terms the results of cognitive and psycho-sociological studies, formulating two possible future research projects: Behavioral Consistency and Group Membership and Inductive Reasoning.