The Grunts cannot speak properly, owing to their inability to move what is left of their lower jaw and their apparent lack of a tongue. However, they are still capable of emitting a range of guttural growls, hisses and noises. Upon paying close attention, their growls sound like an attempt at normal speech, for if it notices the player, it may make a garbled attempt to say "I see you." Their visual and auditory perception appears to be unimpaired though, as they can easily notice Daniel if he is within viewing or hearing range. Staring at them will reduce sanity. Sometimes while idle, Grunts can be seen and heard scratching themselves or whimpering, as if crying. Their initial growl is the signal that they hear Daniel and are coming to investigate. Daniel can withstand a couple of blows from a Grunt, and while they are difficult to outrun when they see Daniel fully, they do get confused fairly easily and thrown off the chase. Laudanum should be taken if a Grunt hits Daniel.
The intelligence of the Grunts is questionable, as they are rather inefficient at searching areas. They will also not notice Daniel if he is standing still and his head is not in view, unless there is a nearby light source such as a candle. They can even be thrown off if Daniel hides behind a door or other object, even if it is obvious (to a functioning human) that Daniel is there. It does seem that Grunts have some intelligence, though, and perhaps emotions; if Daniel makes a loud noise, the Grunt may turn to look in fright with its hands to its mouth before searching.