I think that both texts make use of the ordinary and the possible building to the bizarre and unusual in terms of suspense techniques. Each text has a lead up to the murder in ordinary domestic circumstances that are capitalized on by the killers. Each text takes a basic area of vulnerability the reader could experience and then extends that fear to a terrifying conclusion.
The narrator in The Tell Tale Heart tells us he is mad when reflecting on the events of the story, but we can believe that his behaviour towards his victim would have appeared normal in the lead up to the crime. He tells us that he liked the old man, but his calm observation of the old man with the ‘vulture eye’ becomes a sinister possibility that could have involved many of the readership of the time. Being observed whilst asleep is a latent fear that many readers could have.
Similarly, Norman Bates appears calm and gentle, if a little diffident. His entry into the motel room and his stabbing of Marion is a credible, if unpleasant, scene. As with Poe’s story, the shock of the shower scene is its credibility given the characters involved. The violation of privacy that Marion experiences is another latent fear – the stabbing just compounds the terror.