Towers of Hanoi and London: Is the nonshared variance due to differences in task administration?

Although it has been assumed that the Tower of Hanoi and Tower of London ar e more or less interchangeable tasks dependent on executive function, a ser ies of studies in our laboratory have indicated substantial nonshared varia nce between the performances on the two tasks. The purpose of the present s tudy was to examine how much methods of administration, such as number of t rials per problem, contribute to this nonshared variance. A new one trial v ersion of the Tower of Hanoi was developed to be identical to the Tower of London in four procedural characteristics. The one-trial version of the Tow er of Hanoi was administered to 39 normal adults along with the traditional Tower of Hanoi and the Tower of London-Revised in two test sessions 5-7 we eks apart. The correlations between the two tasks were in the same range as found previously with the traditional task, indicating that administration differences do nor account for the nonshared valiance between the tasks. A reliability analysis of the one-trial tasks showed poor internal consisten cy. Also, the internal consistency of the G-trial tower was artificially in flated by aspects of the administration and scoring procedures. Moreover, t his task exhibited a ceiling effect on repeated testing. These results sugg est that it would be of value to redesign the one-trial Tower of Hanoi syst ematically to increase its reliability and, potentially, its validity as a measure of executive functions.