Mental Steps in Sudoku: Exclusion and Inclusion Tactics

The present study aimed to replicate and extend the unexpected finding of the Lee et al. study (2008) that inexperienced individuals employ exclusion tactics more than inclusion tactics in solving Sudoku puzzles. In Experiment 1, inexperienced and experienced participants were asked to infer the value of a target cell in each of different puzzles. The target cells required use of one of three tactics: exclusion, inclusion and advanced tactics. In addition, the target cells were presented (1) in the puzzles containing only the digits that have to be used in a tactic (non-distracter condition) and (2) in the puzzles with distracter digits. Experiment 2 examined whether or not the instructions given to participants in Sudoku puzzles create a bias towards to superior use of exclusion tactics. The results showed that the experienced participants were better at using inclusion tactics than the naive participants but both the experienced and the inexperienced participants employed exclusion tactics equally well. It was also found that the superior use of exclusion tactics was not due to a biasing affect of the information given in the instructions, supporting Lee et al.'s view that mental steps followed in performing an exclusion tactic are easier than those required by an inclusion tactic