The role of attack and defense semantics in skilled players' memory for chess positions.

There is much evidence that chess skill is based on chunks in memory that represent parts of positions from previously encountered games. However, the content of these chunks is a matter for debate. According to one view, (1) the closer two pieces are to each other on a board (proximity), the more likely they are to be in the same chunk, and (2) skilled players encode the precise locations of pieces. An alternative view is that what information is encoded in a chess chunk is determined more by processing of the attack/defense relations during evaluation. In three experiments, participants evaluated positions and completed recognition tests. Experiment 1 supported the view that expert players make more use of attack/defense relations than of locations of pieces in a recognition test. Experiments 2 and 3 demonstrated that, for both long and short presentation times, expert players' recognition for a piece within a position was primed more by a piece related by attack or defense than by a piece merely proximal. These findings challenge theories of expertise for chess that assume a primary role for proximity and location in determining which pieces are grouped together in memory.