Demonstrated the effects of semantic similarity on the judgment of word meanings in 2 experiments with 10 undergraduates each. Exp. I showed that semantic similarity facilitated the judgment of meaning equivalence, e.g., the judgment that 2 words belong to the same category. Exp. II showed that semantic similarity hindered the judgment of meaning difference, e.g., the differentiation between the meanings of 2 words. Explanations of the effects in terms of associative biases and hierarchical processing are proposed. (PsycINFO Database Record (c) 2006 APA, all rights reserved)