Culture is based on the uniquely human capacity to classify experiences, encode such classifications symbolically, and teach such abstractions to others. It is usually acquired through enculturation, the process through which an older generation induces and compels a younger generation to reproduce the established lifestyle; consequently, culture is embedded in a person's way of life. Culture is difficult to quantify, because it frequently exists at an unconscious level, or at least tends to be so pervasive that it escapes everyday thought. This is one reason that anthropologists tend to be skeptical of theorists who attempt to study their own culture. Anthropologists employ fieldwork and comparative, or cross-cultural, methods to study various cultures. Ethnographies may be produced from intensive study of another culture, usually involving protracted periods of living among a group. Ethnographic fieldwork generally involves the investigator assuming the role of participant-observer: gathering data by conversing and interacting with people in a natural manner and by observing people's behavior unobstrusively. Ethnologies use specialized monographs in order to draw comparisons among various cultures.