Following a right hemisphere stroke, a woman has left-sided paralysis and sensory loss. She acknowledges that the arm lying beside her cannot move, but insists with complete conviction that it is not her own arm — she says it belongs to the nurse and was left there by mistake. What is this?

This is somatoparaphrenia: a confidently held false belief that a limb does not belong to the person, often with a specific alternative explanation of whose limb it supposedly is, typically alongside paralysis and sensory loss following a right hemisphere lesion. It is not anosognosia, which denies that a deficit such as paralysis exists at all — here she accepts the arm is impaired, she simply denies it is hers. It is not hemiasomatognosia, which is a passive lack of felt ownership rather than an active, elaborated false belief about whose limb it is. And it is not a delusion of persecution, since there is no belief of being targeted or harmed here, only a false belief about the arm's ownership.