Trolls não têm cérebro. O livro "Fantastic Beasts and Where to Find Them" deixa bem claro que alguns trolls são mais espertos do que outros e alguns são até capazes de levando uma conversa decente.
Desde que você encontre um interlocutor que não se importe com a possibilidade de ser espancado até a morte, eles podem se provar uma fonte útil de informações sobre qualquer coisa que ocorra em seus territórios montanhosos ou florestais.
Trolls generally converse in grunts that appear to constitute a crude language, though some have been known to understand and even to speak a few simple human words. The more intelligent of the species have been trained as guardians.
De fato, alguns trolls menores parecem ter sido suficientemente confiáveis para se relacionar com crianças
...the Fat Lady was back. She had been expertly restored, but was still extremely nervous, and had only agreed to return to her job on condition that she was given extra protection.
A bunch of surly security trolls had been hired to guard her. They paced the corridor in a menacing group, talking in grunts and comparing the size of their clubs.
Harry Potter and the The Prisoner of Azkaban - – CHAPTER FOURTEEN: Snape’s Grudge