A cognitive analysis of planning performance in the Tower of London task
The Tower of London (TOL) task has been widely used as a measure planning ability in cognitive and neuropsychological settings. In the current study, healthy participants used different planning manipulations to preplan a sequence of moves to match a set of discs to a goal set, then to execute the moves following the plan. The effect of different planning manipulations and trial (puzzle) types on accurate performance was explored across the four experiments in the current study. The effect of the concurrent think aloud at different stages of the planning process in the TOL task was investigated in experiment 1. The results showed that think aloud did not disrupt or enhance performance in the TOL task. The effect of trial difficulty and the contribution of fluid intelligence to planning were explored in experiment 2. Trial type had a greater effect on planning, moving and solving the task with the minimum number of moves. Participants with high fluid intelligence tended to be faster in their planning, recall and execution of their planned moves, and solved the most demanding trial with fewer moves than did their counterparts. The contributions of working memory and intellectual ability in solving a more demanding task such as the Tower of Hanoi (TOH), and its correlation with the Tower of London were examined in experiment 3. The TOL and TOH tasks correlated significantly but only in terms of execution time. It was found that higher intellectual ability and better spatial memory capacity contributed to some aspects of performance on the two Tower tasks. In terms of the TOH task, the results revealed that prolonged planning time in the demanding 5-TOH problem was associated with higher intellectual ability. Moreover, the better ability to estimate the minimum number of moves required to solve the 5-TOH problem might be attributable to a higher intellectual ability and greater spatial memory capacity.