Final answer:
Jane Goodall primarily used naturalistic observation to study chimpanzees, spending extensive time watching them in their natural habitat to understand their behavior and social structures.
Step-by-step explanation:
Jane Goodall is renowned for her groundbreaking research on chimpanzee behavior. The research method she primarily used while studying chimpanzees is observation. Goodall's approach was to immerse herself in the chimpanzees' natural habitat and observe their behavior without interfering. Through her careful and prolonged observations, she was able to gain unprecedented insights into the daily lives, social structures, and behaviors of chimpanzees, such as their use of tools for termite fishing.
Goodall's method aligns with naturalistic observation, a research strategy often utilized in the field of biology and anthropology to study the behavior of organisms in their natural environment. Her meticulous technique set a standard for ethological fieldwork and has inspired numerous subsequent studies relying on observation as a key research method.