Abstract: People are generally faster and more accurate to name or categorize objects at the basic level (e.g., dog), which is known as basic level effect. Previous researchers interpreted basic level effect as the comprehensive effects of steep rise of within- category similarity and slow rise of between-category similarity. But such an explanation can’t explain why People are sometimes faster and more accurate to name or categorize objects at the subordinate (e.g., pigeon).
An operational method of computing the comprehensive effects was put forward in this study, which was called Scores of Category Specificity and defined as the difference between inferior between-category similarity and superior between-category similarity. We suggested that the category whose score was relatively high in its category series would show classifying advantages.
Weather the scores could predict people’s classifying performance at basic-level categories was tested in Experiment 1. The results showed that subjects performed faster and more accurately at basic level in classifying tasks when the scores of basic-level categories were relatively high and that on the contrary was not true. In Experiment 2, we computing the scores of subordinate categories which had been proved that people were faster and more accurate to name or categorize objects at and referred to as special cases in previous studies. The results showed that people performed faster and more accurately at these subordinate categories just because the scores of these categories were relatively high, rather than interpreted as special cases. We found at the same time that specificity of subordinate categories had an impact on the scores. In Experiment 3, we further explored whether people had different performance when the same basic level category was combined with subordinate categories of different specificity. The results showed that people were faster and more accurate at basic level categories if they were combined with subordinate categories with low specificity and that people were faster and more accurate at subordinate categories if basic level categories were combined with subordinate categories with high specificity.
Scores of Category Specificity were an effective indicator to predict at which level of categories people performed better in classifying tasks. The reason why scores of levels of categories varied was that people formed different degree of representational specificity according to various levels of taxonomical series in daily experience, which was known as Experience Theory.

Key words: basic-level category, subordinate category, similarity, scores of category specificity, classifying advantage, experience theory