Many historians consider Japanese civilization developing along a distinct track against that of the Asian mainland and in particular, China, since the Heian period (794 – 1185). They believe the Japanese then began to shift their attitude toward Chinese civilization from assimilating at full scale to selectively adopting, and to gradually nurture and accumulate their native cultural tradition (a.k.a. kokuhubunka in Japanese). Selectively adopting implies that the Japanese central authority mainly focused on domestic affairs, while still kept an eye on the development of China and imported any of her achievements which might benefit the Japanese state. According to that theory, many argue that the subsequent Chinese dynasties and her tributary states then made much less external impact on Japan, both her society and people, in the recent millennium; Japan would often tend to stay indifferently away from the movement and conflict in mainland Asia. Particularly during the Tokugawa period, a period considered by historians as the most isolated time in Japanese history, even though some dramatic changes took place in China and East Asia, many believe the Japanese still lived in their own world pacifically.