Abstract: The current study examined the effect of the property of stimulus’ feature on category. Participants in the research consisted of 180 senior under-graduates in South China Normal University. The materials included learning materials and testing materials. And the learning materials were a sample sheet depicting 12 members of two categories, 6 for each category. The testing materials included many new stimuli which are different from the members in the sample sheet in similarity and rivalrousness. Participants were supposed to predict the category label of each stimulus based on the group defined in the sample sheet. The proportion of category-accordance response and the confidence of the response were analyzed. The results of the two experiments showed that: (1) as the two components of similarity, the number of matching features and their matching probability were in direct proportion with the accordance and confidence of the response;(2) as the two components of rivalrousness, the number of rivalrous features and their rivalrous probability were in inverse proportion with the accordance and confidence of the response

Key words: category, similarity, rivalrousness, probability of features