The rhetorical device of "personification" is one in which inanimate objects are given the attributes of people, such as emotions, thoughts, etc. If we describe a house as "inviting" or a gun as "threatening"or a landscape as "gloomy" we are projecting emotions onto objects which themselves are incapable of feeling. Writers do this to evoke emotions, often as a way of externalizing a character's state of mind. For example, a common form of personification is a form of the pathetic fallacy, in which the weather expresses a character's mood (see, e.g. Tennyson's Mariana in the Moated Grange or Rizpah)
One sign of the insanity of the tale's narrator is the way he constantly projects his own fears on external objects. This simultaneoulsy evokes a sense of horror and reveals to us the narrator's own paranoia.