Most basically, we learn to speak a language both because we are genetically programmed to do so and because we are surrounded from birth by people speaking to and about us. We are supposed to pick up a lot of knowledge about social interactions and how the world works in the same sort of way but not all of us are equally good at this!
Nicholas van Rijn, David Falkayn and Dominic Flandry learn quickly and soon are able to operate effectively in the world as they find it.
"'And I thought I was your first,' she said.
"'Why, Persis!' he grinned.
"'I felt so - and every minute this evening you knew exactly what you were doing.'"
-Poul Anderson, Ensign Flandry IN Anderson, Young Flandry (Riverdale, NY, 2010), pp. 1-192 AT Chapter Nine, p. 87.
"[Abrams'] aide, Flandry, looked alert; but he was young and very junior." (Chapter Ten, p. 94)
"[Flandry] grew conscious, then, of what power meant, how it worked. You kept the initiative. The other fellow's instinct was to obey, unless he was trained in self-mastery. But you dared not slack off the pressure for a second. Hauksberg slumped in his seat and gave no trouble." (Chapter Thirteen, p. 136)
"'Commander,' [Brechdan Ironrede] said, 'your young man makes me proud to be a sentient creature. What might our united races not accomplish? Hunt well.'" (Chapter Fourteen, p. 145)
"...[Kossara] sensed alertness beneath [Flandry's] relaxed manner."
-Poul Anderson, A Knight Of Ghosts And Shadows IN Anderson, Sir Dominic Flandry: The Last Knight Of Terra (Riverdale, NY, 2012), pp. 339-606 AT Chapter IV, p. 392.
Alert and learning throughout life.