Statistical methods employed to test individual differences in dual-task performance and the existence of a general time-sharing ability are reviewed and critiqued. Specifically, both the types of data being collected and the types of data analysis procedures have been inadequate to the critical evaluation of a hypothetical…

The development of a probabilistic model for validating Gange's learning hierarchies is described. Learning hierarchies are defined as paired networks of intellectual tasks arranged so that a substantial amount of positive transfer occurs from tasks in a lower position to connected ones in a higher position. This probabilistic validation technique…