By the final chapter of the novel, "At Harry's," Patrick's mental state has deteriorated severely, to the point where he has to repeat his favorite drinks, TV shows, and sports to himself to keep a grip on reality. In this barely coherent state, he describes a series of hallucinations that he has recently experienced:
I’m having a sort of hard time paying attention because my automated teller has started speaking to me, sometimes actually leaving weird messages on the screen, in green lettering, like “Cause a Terrible Scene at Sotheby’s” or “Kill the President” or “Feed Me a Stray Cat,” and I was freaked out by the park bench that followed me for six blocks last Monday evening and it too spoke to me. Disintegration—I’m taking it in stride.
Patrick recounts both an ATM and a park bench speaking to him. Thanks to Patrick's unclear narration, the reader could interpret these either as personification or anthropomorphism. The author of a more typical novel might use this passage as personification, making inanimate objects come to life merely as a nonliteral way to describe Patrick's feelings. But given Patrick's near-constant hallucinations, it seems that he really believes that these things are speaking to him. This, then, is arguably an example of anthropomorphism, in which nonhuman things literally do humanlike actions. The incoherent state of the narration results in this ambiguous interpretation.
This passage also shows how Patrick's hallucinations get more severe over time. The first one is more simple: the automated teller, such an important checkpoint for Patrick throughout the novel, now begins to tell him to do terrible things. This conflicts with Patrick's usual assertions that he is entirely alone and that he commits his murders entirely on his own whims. But this is not an especially extreme instance of personification: while the machine makes requests like a human might, it is still only displaying text on a screen like any normal ATM does. The park bench, though, is more ridiculous. It runs on its metal legs, chasing him, which no park bench can do. Patrick's hallucinations get further from reality. By this point near the end of the novel, Patrick's deluded perception and memory, combined with Carnes's claim that he saw Paul Owen alive in London, makes the reader doubt whether any of the events of the narrative really happened.