PERCEPTION IN CHESS William G. Chase Herbert A. Simon
Since De Groot's experiment chess masters' perception has been in the spotlight. And it seems pretty much clear that masters seem to perceive chess positions as chunks of several RELATED pieces.
In this article from 1973 the authors revisit De Groot's experiment trying to lay out a solid base for the chunking theory.
Once again, the master outperformed amateur and beginner in LEGAL positions. But not in random (NON-legal) positions.
This led to think that memory of positions depends on recognizing familiar configurations of pieces (a.k.a. chunks).
Several hypothesis where used:
Chunking theory states that perception and long term memory are developed all together and thus experts and novices do not perceive the same thing when exposed to the same situation.