Trolls are generally considered to be of lower intellect than most other species. They certainly have some cognitive abilities, and are capable of using language and have some writing skills, but they consistently use very poor grammar, and grunts are very common in their communications.
They also do not appear to have a deep understanding of the world around them. Some Swamp Trolls have even setup a shrine to a Football in their cave.
A witch near Kazordoon is currently doing some research on breeding trolls, but it is unknown what purpose this will serve.