Cognition, Brain, Behavior. An Interdisciplinary Journal Copyright © 2018 ASCR Publishing House. All rights reserved. ISSN: Print 2247-9228, Online 2601-226X Volume XXII, No. 4 (December), 197-213 doi:10.24193/cbb.2018.22.13 Taxonomic and thematic categorizations from preschool years to adulthood: Looking behind the choices Asimina M. Ralli * , Kalomira A. Niasti Department of Psychology, National and Kapodistrian University of Athens, Athens, Greece Abstract Categorization constitutes the most important function of information’s semantic organization in the memory system. Semantic organization refers to the way in which a person organizes the knowledge making sense of the world, while it also constitutes a vital part of language acquisition. One of the basic roles of categorization is to provide the cognitive system with high efficiency, whenever it encounters a vast amount of information in the environment. The aim of this study was to investigate types of categorization, and more specifically taxonomic and thematic pairings from preschool years to adulthood, using a cross-sectional design. One hundred and fifty (N =150) participants from five different age groups (3-years old, 6-years old, 9 years old, 13 years-old and 20 years-old) participated in the study. A categorization task was administered to all the participants. Each participant was presented with a target item and three other associate items (thematic, taxonomic and irrelevant). Then, he/she was asked to choose the one that «went best with the target item» and to justify the pairings. According to the results, the younger participants tended to create groups of items according to thematic associations, while older participants created groups of items on a taxonomic basis. Additionally, the type of justifications varied by age. Younger participants did not provide any justification or if they did, it was a thematic justification, while older participants used mainly taxonomic justifications. Keywords: categorization skills, taxonomic choices, thematic choices, justifications Object categorization is one of the most important and adaptive activities of human cognition. Not only do categories allow someone to function efficiently by organizing knowledge about the environment, but they are also one of the means to infer properties of objects on the basis of their categorical belonging (Blaye, Chevalier, & Paour, 2007). Categorization refers to the ability of grouping equivalent concepts, experiences, objects or events, based on similarities, which * Corresponding author: E-mail: asralli@psych.uoa.gr