Aptitude tests › Planning puzzles

Planning puzzles: the Tower of London and how to practise

Some game-based assessments include a planning puzzle: coloured pieces on pegs or sticks, and you rearrange them into a target pattern in as few moves as you can. The classic is the Tower of London, a task built by the psychologist Tim Shallice in 1982 to measure planning. Versions used in hiring can be timed and scored on speed as well as accuracy. Either way, the puzzle looks at whether you plan ahead or move by trial and error.

What the puzzles look like

• Tower of London: a few balls or discs on pegs that hold different numbers of pieces. Move them one at a time to match a target, often in a stated number of moves.
• Colour sorting: coloured pieces mixed up on sticks or in tubes, with a spare stick or two. Sort them so each stick holds one colour. Practise with doughnut sort.

How they're scored

In research on the Tower of London, the usual measures are how many moves you needed against the fewest possible, and how long you took, both before the first move and during the solution. Assume every move counts on the day, including any you undo. So the cheapest way to a good score is to think before you touch anything.

How to prepare

1. Count the floor first. In a sorting puzzle, count the groups of one colour sitting together. That number minus the number of colours is the floor: nobody can solve it in fewer moves. The planning guide shows why, with a worked example.
2. Look for free moves. A move that joins two groups of the same colour costs nothing extra. Moves onto an empty peg do.
3. Plan the first few moves, at least until the first colour or peg is finished, then pause again wherever more than one move looks reasonable.
4. Practise under the same rules: moves counted, undos included, so your habits match the real test.

Start now

Doughnut sort is free at all six levels, with no account needed. Every puzzle shows the fewest moves possible, worked out exactly, so you always know how close you came.

See also what employers' games measure.

preplaud is not affiliated with or endorsed by any test publisher. The puzzles described here are a general kind, practised here with our own.