Linguistic relativity studies have experienced a resurgence since the 1990s, and a series of favorable experimental results have brought Whorfianism back into favor, especially in cultural psychology and linguistic anthropology. The first study directing positive attention towards Whorf's relativist position was George Lakoff's "Women, Fire and Dangerous Things", in which he argued that Whorf had been on the right track in his focus on differences in grammatical and lexical categories as a source of differences in conceptualization. In 1992 psychologist John A. Lucy published two books on the topic, one analyzing the intellectual genealogy of the hypothesis, arguing that previous studies had failed to appreciate the subtleties of Whorf's thinking; they had been unable to formulate a research agenda that would actually test Whorf's claims. Lucy proposed a new research design so that the hypothesis of linguistic relativity could be tested empirically, and to avoid the pitfalls of earlier studies which Lucy claimed had tended to presuppose the universality of the categories they were studying. His second book was an empirical study of the relation between grammatical categories and cognition in the Yucatec Maya language of Mexico.