A core component of social functioning is the capacity to attribute mental states to others and to understand intention as psychologic cause. The hypothesis of this study was that dementia of the Alzheimer type
(DAT) patients show an impaired understanding of psychologic cause although they remain able to understand physical causality.
To test this hypothesis, 20 elderly adults with DAT, 20 healthy age-matched controls, and 20 healthy young adults were presented a cartoon task requiring them to process physical or psychologic cause of events.
Patients with DAT at onset scored significantly lower than controls when they had to reason about psychologic causation, while they did not differ for reasoning about physical causation. Consistent with these results, patients with DAT showed significantly lower scores in psychologic reasoning as compared with their scores for physical causality. Instead young and elderly healthy adults scored similarly for the 2 types of causality and the 2 groups did not differ in their scores. These results suggest that impaired understanding of intention in others may be considered as an early socio-cognitive index of onset of DAT. A post hoc division of the group of patients with DAT into 2 subgroups according to Mini Mental State (MMS) scores showed that the group with the more severe MMS scores not only had lower scores for psychologic causality but also showed impairment in reasoning about physical causality involving persons. Physical causality involving objects remained relatively preserved.
The remarkable deficit in attribution of intention in our patients with DAT at onset and the following deterioration of their performance in reasoning about physical causality with persons may reflect progressive dysfunction of the superior temporal sulcus in Alzheimer disease.