Toys and gadgets: construct validity of apathy in Parkinson's disease.

Apathy is one of the primary neuropsychiatric signatures in Parkinson's disease, yet little research has addressed the construct validity of two commonly used apathy measures, the Apathy Scale and the Lille Apathy Rating Scale. The authors tested the hypothesis that apathy is associated with reduced initiative/engaged behaviors on a laboratory-based measure of apathy. Support was found for the hypothesis that apathy, as indexed by the Apathy Scale and the Lille Apathy Rating Scale, is associated with reduced initiative/engagement on an experimental measure of apathy in Parkinson's disease patients. These findings provide independent evidence for the construct validity of self-report apathy scales, beyond clinician judgment.