The ability to categorize has been known as one of the most important cognitive abilities in human beings. When it comes to the topic of categorization type, it seems different people select differently. Some of them categorize on the basis of similarity judgment and some based on the uni-dimensional rule. The present study attempts to evaluate the tendency toward a specific type of categorization as can be observed in a voluntary group of medical students in Iran. Most of the studies in categorization have been conducted in Western world and some of Eastern-Asian people. To the best of our knowledge, this is the first study which has been done in categorization in Iran. The results suggest that Iranians, like Eastern-Asian people, tend to categorize mostly based on similarity. There was not any relationship between the IQ scores of the participants and the type of categorization. We also examined the implications of the words “similarity” and “belonging to” as translated into Persian.