An experiment was conducted to investigate the nature of synonyms by using multidimensional scaling. The selected concept was "pig" and three of its synonyms--"hog,""boar," and "swine." These terms vary in their frequency of use in English, which makes it possible to explore a behaviorally based theory of meaning. Subjects were randomly assigned to one of four conditions where they performed direct pair comparisons with one of the four "pig" terms, a series of barnyard animal names, attributes, and a concept of self. The means of these four groups were entered into a multidimensional analysis. In contrast to the logical assumption that synonymous words would produce identical multidimesional spaces, the results, in fact, suggest that the four "pig" terms are not really equivalent, varying systematically in their meanings, in their use, and in their relation to positive attributes. The systematic variance in their meanings is such that each concept's distance from self on the multidimensional scale is inversely related to the frequency at which the concept is used in English. This further suggests that meaning is behaviorally governed, and that any symbol's meaning is an empirical question whose answer depends on measuring the actual users of that symbol. (Author/RL)