Final answer:
The reading materials do not specifically mention Chagnon or the Yanomamo. Chagnon faced difficulties with his fieldwork due to the Yanomamo's habit of providing false information that complicated understanding their social structure.
Step-by-step explanation:
In the provided reading materials, there is no direct mention of anthropologist Napoleon Chagnon or the specific habit of the Yanomamo that made his fieldwork difficult. However, from existing knowledge, Chagnon noted in his work that a challenging habit he encountered while studying the Yanomamo was their practice of deliberately giving false information or using kinship terms that confused genealogical data. This habit made it challenging for Chagnon to construct accurate kinship diagrams and understand the social structure of the tribe at first, significantly complicating his early fieldwork.