Book excerpt: John Lucy uses original, empirical data to examine the Sapir-Whorf linguistic relativity hypothesis: the proposal that the grammar of the particular language that we speak affects the way we think about reality. The author compares the grammar of American English with that of the Yucatec Maya, an indigenous language spoken in Southeastern Mexico, focusing on differences in the number marking patterns of the two languages. He then identifies distinctive patterns of thought relating to these differences by means of a systematic assessment of memory and classification preferences among speakers of both languages.