category. This approach, which Lucy later classified as domain-centered, is acknowledged to be sub-optimal, because color perception, unlike other semantic domains, is hardwired into the neural system and as such is subject to more universal restrictions than other semantic domains. In a similar study done by German ophthalmologist Hugo Magnus, he circulated a questionnaire to missionaries and traders with ten standardized color samples and instructions for using them in the 1870s. These instructions contained an explicit warning that failure of a language to distinguish lexically between two colors did not necessarily imply that speakers of that language did not distinguish the two colors perceptually. Magnus received completed questionnaires on twenty-five African, fifteen Asian, three Australian, and two European languages. He concluded in part, ‘As regards the range of the color sense of the primitive peoples tested with our questionnaire, it appears in general to remain within the same bounds as the color sense of the civilized nations. At least, we could not establish a complete lack of the perception of the so-called main colors as a special racial characteristic of any one of the tribes investigated for us. We consider red, yellow, green, and blue as the main representatives of the colors of long and short wavelength; among the tribes we tested not a one lacks the knowledge of any of these four colors’ (Magnus 1880, p. 6, as trans. in Berlin and Kay 1969, p. 141). Magnus did find widespread lexical neutralization of green and blue, that is, a single word covering both these colors, as have all subsequent comparative studies of color lexicons. Brown and Lenneberg's study began a tradition of investigation of linguistic relativity through color terminology. The studies showed a correlation between color term numbers and ease of recall in both Zuni and English speakers. Researchers attributed this to focal colors having higher codability than less focal colors, and not with linguistic relativity effects. Berlin/Kay found universal typological color principles that are determined by biological rather than linguistic factors. This study sparked studies into typological universals of color terminology. Researchers such as Lucy, Saunders and Levinson argued that Berlin and Kay's study does not refute linguistic relativity in color naming, because of unsupported assumptions in their study (such as whether all cultures in fact have a clearly defined category of "color") and because of related data problems. Researchers such as Maclaury continued investigation into color naming.