Intution, pattern matching, fast thinking.
Developing driving reflexes (“system 1”) only happens after sufficient practice with “system 2” rules in mind - hence the slow uncertainty of learning drivers (hopefully). Sudoku is similar - at first, you check sums. Then you develop rules. Then for simple rules you develop reflexive thinking (“system 1” for the cool kids).
… so system-1, intuition, can be trained / expanded to new areas.