Tower of London
Rearrange balls in minimum moves
About this trainer
The Tower of London is a planning puzzle with three coloured balls sitting on three pegs that hold a different number of balls (one, two and three). You are shown a goal arrangement and have to move the balls, one at a time and only the topmost ball on a peg, until your board matches the goal in as few moves as possible.
What it develops
It exercises planning and look-ahead: holding a goal in mind, mentally simulating a sequence of moves before you touch anything, and resisting the obvious first move when it leads to a dead end. Working memory and impulse control come along for the ride.
History
It grew out of clinical neuropsychology rather than games. Tim Shallice introduced it in 1982 to measure planning deficits in patients with frontal-lobe damage, and it was quickly picked up by test batteries, became a fixture in brain-imaging studies of the prefrontal cortex, and spread into apps and brain-training collections.
Who created it — and when
Created by the British neuropsychologist Tim Shallice in 1982, in his paper Specific impairments of planning (Philosophical Transactions of the Royal Society of London). It is a deliberate simplification of the older Tower of Hanoi puzzle, which the French mathematician Edouard Lucas published in 1883.
How to train
Plan the whole sequence before your first move rather than nudging balls and hoping. Work backwards from the goal, ask which ball must end up on the bottom of each peg, and watch for moves that temporarily take you further from the goal but are unavoidable. Tracking the minimum-move count for each puzzle keeps you honest.
How long to practise
Short focused sets work best: five to ten minutes, a few puzzles of rising difficulty, a few times a week. It is mentally taxing, so quality of planning matters far more than volume, and there is little point grinding it for an hour.
Evidence base
What is solidly shown is narrow: people get better at the Tower of London itself, and the task is a genuinely sensitive clinical measure of planning that is impaired after prefrontal damage and in several conditions. The popular leap from practising it to broadly sharper everyday planning, higher intelligence or protection against cognitive decline is weak and largely unproven, so treat far-reaching transfer claims with caution.
Recommendations
Pause and plan the full route in your head before the first move, then execute without second-guessing, and only then check how close you came to the minimum.
FAQ
Is the Tower of London the same as the Tower of Hanoi?
No. The Tower of Hanoi uses discs of different sizes that must always stay in size order, while the Tower of London uses same-sized balls and pegs that hold only one, two or three balls. They look alike but stress planning in slightly different ways.
Will practising this make me better at planning in real life?
It reliably makes you better at the puzzle, and it is a respected clinical test of planning. But strong carry-over to organising your day or projects has not been convincingly demonstrated, so enjoy it as focused practice rather than a guaranteed life upgrade.
What counts as a good result?
Solving each board in the minimum number of moves, ideally after planning the sequence in your head rather than by trial and error. Taking a few seconds to think before the first move and then needing few corrections is a better sign than fast, frantic shuffling.
Variants
Close relatives include the Tower of Hanoi (size-ordered discs instead of capacity-limited pegs), the Stockings of Cambridge in the CANTAB battery, the Drexel Tower of London (ToL-DX), the Tower Test in the D-KEFS, and the Freiburg TOL-F. Versions differ in the number of balls or discs, peg layout and how strictly planning time is separated from execution time.