Comparing alternative metrics to assess performance on the Iowa Gambling Task

This study was conducted in response to calls to develop Iowa Gambling Task (IGT) metrics reflecting more homogeneous aspects of decision making, as well as to add to the literature on reliability and validity of the instrument. The conventional IGT metric, advantageous minus disadvantageous deck selections, was compared to alternatives in which Decks B and C or the first 40 selections were eliminated. We correlated these alternative metrics with performance on other neuropsychological tests in 214 healthy adults, and we compared participant subgroups stratified by health status (214 healthy and 43 unhealthy participants). Internal consistency of the IGT was low and could explain the modest levels of construct validity observed. Alternative metrics, especially Deck D minus Deck A selections (D-A), did improve construct and criterion validity of the IGT. They also showed different patterns of correlation with other neuropsychological measures and might enhance the clinical and scientific usefulness of this test. Future research with an eye to modifying the paradigm and/or administration procedures to increase intertrial consistency might also give a needed boost to construct and criterion validity.