A 72-year-old woman with no prior psychiatric history is brought in by her daughter, who reports that over the past 3 months her mother has developed persistent beliefs that neighbors are entering her home at night and rearranging her furniture. The patient is alert, oriented to person, place, time, and situation, and her cognition on bedside testing is intact with a Montreal Cognitive Assessment (MoCA) score of 27/30. Her medical workup including CBC, CMP, thyroid panel, urinalysis, and brain MRI are unremarkable. She maintains her daily routine and self-care but has become increasingly isolated due to her suspicions. Which assessment finding most strongly supports a diagnosis of very late-onset schizophrenia-like psychosis over delirium?