The riddle of anosognosia: A second look at overconfidence in unawareness of hemiparesis with two riddle tasks.

Anosognosia, a lack of awareness of a neurological deficit, is a multi-component disorder involving coexisting neurological and cognitive impairments. Patients with anosognosia for hemiparesis fail to use new information about their bodily self to update beliefs. Overconfidence in situations of uncertainty and a failure to adjust beliefs in a verbal riddle task have been identified in a previous case series. This prospective study extends these findings using the same verbal riddle task and an additional non-verbal picture riddle task in 41 stroke patients and 22 age-matched controls. Each riddle contains five clues leading to a target word or picture. After each clue, participants provide a guess and a confidence rating. All riddles are designed to create an initial situation of uncertainty. The picture riddle is simpler and less dependent on language and memory capacities. In our cohort, 14 out of 41 patients were unaware of their paresis. Contrary to prior work, we found the riddle paradigm to be unsuitable for measuring belief-updating. Regarding overconfidence, the level of confidence for the first two clues differed significantly between patients with anosognosia and controls, but not between patients with and without deficit awareness in the word riddle. In the picture riddle, patients with anosognosia had significantly higher confidence levels than the other subgroups. To conclude, overconfidence was most common in patients with anosognosia but was not exclusive to them.