He borrows terms from linguistics: just as a phon-etic system is a description of sounds developed without regard to the meaning and structure of the language, while a phon-emic system describes the meaningful sounds actually used within the language, so anthropological data can be emic and etic. Only trained observers can avoid eticism, or description without regard to the meaning in the culture: "... etics are in part observers' emics incorrectly applied to a foreign system..." He makes a further distinction between synchronic and diachronic. Synchronic ("same time") with reference to anthropological data is contemporaneous and cross-cultural. Diachronic ("through time") data shows the development of lines through time. Cultural materialism, being a "processually holistic and globally comparative scientific research strategy" must depend for accuracy on all four types of data. Cultural materialism differs from the others by the insertion of culture as the effect. Different material factors produce different cultures.