Consumer behavior is a key part of living in our society: Modern life is typically expressed in consumer acts. Consumer behavior is traditionally studied by the Marketing field, a field that takes into account knowledge of other sciences to enhance their comprehension of this specific behavior. This project?s goal was to investigate consumer behavior from a radical behaviorist perspective according to the principles of Consumer Behavior Analysis, an approach that brings together the theories and findings of marketing and behavior analysis/behavioral economics. The present work?s objectives were: (1) to verify the possibility of identifying the patterns that lead consumers to build a repertoire /subset of brands of fast moving consumer goods (FMCG) through the analysis of the value of utilitarian and informative reinforcers embedded in the products consumed by a group of consumers; (2) to verify if consumers? behaviors are influenced by the same level of utilitarian and informational reinforcers, when the analysis is applied to different product categories of specific consumers (3) to test for generality of the study?s finding by comparing its results with studies conducted in a different country (England). The major goal of marketing executives is to conquer as much loyal consumers as possible (?loyalty? in marketing terms is defined as having a consumer making 100% of his/hers product choices in one specific brand within a product category), but purchasers of fast-moving consumer goods generally exhibit a multi-brand choice. Previous researches showed that consumers tend to select their purchases apparently randomly within a small subset or ?repertoire? of already known and trusted brands. Using panel data for the purchases of 134 consumers buying four product categories of FMCG (deodorant, soap, soda, and cookies) over a 52-week period, the following results were found: (a) the number of loyal consumers was higher than expected from results of previous studies, (b) by using the concepts of utilitarian and informational reinforcers it was possible to identify a pattern that seems to characterize how consumers put together their brand repertoire, (c) that the product brand (a feature correlated with informational reinforcer) seems to exert a stronger influence over the consumers? choices than do the products attributes (correlated with utilitarian reinforcers) for the consumption of the products analyzed in the present study, and (d) that the relevance of utilitarian and informative reinforcers vary among product categories as a determinant of the consumer?s choice