How did Matt know that Attean was becoming his friend?
In the beginning of the story, Matt and Attean are forced into a relationship when Attean's grandfather, Saknis, makes a deal with Matt. He is to teach Attean the English language in return for the provisions and care Saknis provides him.
As the story unfolds, Matt and Attean explore the wilderness together. Attean teaches Matt Indian ways. Matt begins to think that he might be earning Attean's respect, if not his friendship, when Attean tells Matt he acted with the speed and thought of an Indian in protecting them from a bear. Later in the story, Matt is invited to Attean's village by his grandmother where he plays Indian games with the children of the village. Matt reflects at the end of the day that he has finally been accepted as a friend by Attean and the Indians of the village.
Ironically, Matt earns Attean's ultimate respect and friendship when Matt refuses to leave the cabin and travel with Attean and his family to their new home. Though Attean is concerned about his friend alone in the wilderness, he respects his decision to wait for his family and ultimately the two exchange prized possessions. Attean gives Matt his dog. Matt gives Attean his pocket watch.