We examined how mushroom experts organize and process their knowledge, compared with novices, and which types of arguments they use to process information. Mushroom experts and novices carried out an identification/memorization task, a free recall task, and a matching task. Results showed that experts performed better than novices on all three tasks. In the identification task, they named items at the subordinate level, whereas novices named them at the basic level. In the free recall task, experts recalled more items than novices, by grouping them into categories, while in the matching task, they used both similarity and dissimilarity criteria and provided conceptual and perceptual arguments. In conclusion, experts seem capable of carrying out two types of processing: relational processing, reflecting the ability to form categories at the basic level by considering the similarities of items belonging to the same category, and more analytical processing at the subordinate level, reflecting the ability to process difference in a context of similarity, indicating that experts are also able to use specific (distinctive) attributes, relying simultaneously on perceptual and conceptual information.