= Solution
\b[Consider learning and memory of the maps.] Repeating an identical map can improve later scores through recall rather than the assigned program, and a skill learned using one program can transfer to another. Provide comparable familiarization before recording responses and use new, difficulty-matched maps on later afternoons. If all volunteers face the same map on a given afternoon, common map difficulty is absorbed by the afternoon block.
The balanced transitions in the proposed <row-column design> help with first-order <carryover effects>, but general practice, higher-order memory and program-dependent learning may still require an explicit <interaction term> or <carryover effect> in the analysis. Merely applying <randomization> to treatment labels cannot make these effects disappear.
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