Tower of London Task

The Tower of London task is a neuropsychological/cognitive psychology test that assesses planning ability within executive function. Participants must move colored balls from a starting configuration to a target configuration in the minimum number of moves, thereby measuring strategic thinking, working memory, and problem-solving skills.

It primarily measures executive function, especially planning ability, pre-planning, working memory, strategy use, and problem-solving skills.

Participants are shown a target configuration (an arrangement of differently colored balls on pegs/rods) and must then move the balls on another board (or computer interface) to match that target in the fewest moves possible, while following rules such as moving only one ball at a time and not exceeding peg height limits.

Scoring is typically based on several variables: the number of moves taken to solve a problem, whether the minimum number of moves was exceeded (i.e., 'excess moves'), the time taken to complete the task, the initial thinking time (time from problem onset to the first move), and whether rules were violated or extra attempts were used. Fewer moves, shorter times, and better rule adherence yield better scores.

The task is widely used with healthy individuals, children, adults, and populations with neuropsychological or developmental disorders (e.g., ADHD, traumatic brain injury, frontal-lobe damage) to evaluate planning and problem-solving abilities.

The task was originally developed by Tim Shallice in 1982. Since then, multiple variants have emerged, including versions with more balls and pegs, computerized adaptations, child-friendly versions, and shortened formats. Research has shown that cueing, pre-planning, and task difficulty can influence outcomes.

Generally, the closer the number of moves is to the minimum possible, the shorter the time taken, the shorter the initial thinking time, and the fewer rule violations or extra attempts, the stronger the planning ability or executive function. Conversely, poorer performance may indicate difficulties in planning or problem-solving. Interpretation should consider age, education, and version type.

Yes. For example, rules, difficulty, and cueing conditions vary across versions; construct validity has been debated in some studies; and the task may offer limited simulation of real-life planning situations. Therefore, results should be interpreted cautiously.