Tower of Hanoi Test (ToH)

Background

The Tower of Hanoi Task (ToH) is a clasic puzzle created in 1883 by French mathematician Édouard Lucas. The task was adapted by psychologists, most notably Herbert Simon in 1975, to investigate cognitive theories of planning and problem solving. The ToH is a "look-ahead" task that requires a problem to be decomposed into a series of subgoals, some of which may seem to take one further from the final goal.

The task requires respondents to rearrange 3 disks of different colors and sizes from their current positions on 3 pegs to a different configuration with the constraints that only the topmost disk on a peg can be moved, and larger disks can not be placed above smaller disks.

Task Procedure

The participant is presented with gameboard featuring a large, medium, and small blue disk positioned on 3 pegs along with an image of the disk in different positions (the goal). Participants must re-arrange the disks into the goal positions using as few moves as possible.

The participant is presented 1 practice problem and 12 test problems of increasing difficulty. For each problem, a running tally of executed moves is displayed along with the minimum number of required moves (the ideal solution for each problem). A maxixum of 20 moves is allowed before the problem is reset and the participant is asked to try again. After 6 failed attempts on any given problem, the task is terminated.

Participants must solve each test problem twice before advancing to the next problem, regardless of whether they find the ideal solution.

What it Measures

The ToL is not diagnostic of any single condition, but rather a general assessment of executive functioning.

Psychological domains

• Executive Functioning
• Planning: Requires generating and maintaining a plan while looking ahead multiple steps
• Problem-Solving, Strategic Thinking: Identifying the most efficient solution ahead of time rather than through trial-and-error
• Working Memory: Holding and manipulating the current configuration, goal state, and intermediate steps online
• Cognitive Flexibility: Adjusting plans when initial strategies fail
• Inhibitory Control / Response Inhibition: Avoiding moves that seem intuitively correct but violate rules or increase total moves

Main Performance Metrics

• Total Score: Planning efficiency (6 points per problem less the number of failed attempts)
• Total Number of Moves: Planning efficiency
• Mean Planning Time: Speed of planning (latency before the first move)
• Mean Execution Time: Speed of plan implementation (latency between first move and solution)
• Mean Solution Time: Planning and execution time
• Rule Violations: Inhibitory control

Psychiatric Conditions

Performance tends to be impaired in patients with the following conditions.

• Schizophrenia
• Traumatic Brain Injury (TBI)
• Parkinson’s Disease
• Eating Disorders
• Dementia
• Attention Deficit Hyperactivity Disorder (ADHD)
• Autism Spectrum Disorder

Available Test Variations

References

Search Google Scholar for peer-reviewed, published research using the Inquisit Tower of Hanoi Test (ToH).

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Humes, G. E., Welsh, M. C., Retzlaff, P., & Cookson, N. (1997). Towers of Hanoi and London: Reliability and Validity of Two Executive Function Tasks. Assessment (Odessa, Fla.), 4(3), 249–257. https://doi.org/10.1177/107319119700400305

Miyake, A., Friedman, N. P., Emerson, M. J., Witzki, A. H., Howerter, A., & Wager, T. D. (2000). The Unity and Diversity of Executive Functions and Their Contributions to Complex “Frontal Lobe” Tasks: A Latent Variable Analysis. Cognitive Psychology, 41(1), 49–100. https://doi.org/10.1006/cogp.1999.0734

Robinson, S. J., & Brewer, G. (2016). Performance on the traditional and the touch screen, tablet versions of the Corsi Block and the Tower of Hanoi tasks. Computers in Human Behavior, 60, 29–34. https://doi.org/10.1016/j.chb.2016.02.047