memory to rapidly store and retrieve information using long-term memory for
information in their domains of expertise. Building on the distinction between a
limited short-term memory and a vast long-term memory, this theory sees the
key problem to be selective access to information stored in long-term memory.
Skilled-memory theory postulates that at the time of encoding, experts acquire
a set of retrieval cues that are associated in a meaningful way with the infor-
mation to be stored. At a later time, the desired information can be retrieved
from long-term memory by using the appropriate retrieval cue. After extensive
practice using a stable set of retrieval cues with meaningful information in the
domain, one’s speed of encoding and retrieval is assumed to approach that for
short-term memory. The best empirical evidence regarding the structure and
operation of skilled memory comes from studies of subjects who achieved ex-
ceptional levels of performance on the digit-span task (Chase & Ericsson, 1981,
1982; Staszewski, 1987). The retrieval cues used for rapid storage of meaningful
encodings of three- and four-digit groups (up to a total of more than a hundred
digits) can be used to access digits in presented matrices in a manner earlier
believed to require a raw visual image (Ericsson & Chase, 1982). Studies of
other types of expertise have given clear evidence for retrieval cues indexing
content (e.g., specific intermediate products in mental calculation) (Ericsson &
Staszewski, 1989; Staszewski, 1988).
The most direct evidence suggesting the use of retrieval structures in chess
comes from a series of studies with a candidate chess master by Ericsson and
Oliver (Ericsson & Staszewski, 1989). They found that the chess master could
read the description of the sequence of chess moves in a game and mentally
generate the sequence of intermediate chess positions almost as fast as he could
play out similar chess games by actually moving the pieces on a chessboard.
During the process of mentally playing out the chess games, sometimes they
would interrupt him and test his ability to name the piece on a given square for
the current chess position, which he could do within a few seconds. In other
experiments, his speed of access to different types of information for a briefly
presented middle-game chess position was examined. The chess master could
name the piece located on a given square within a second, and within seconds
he could report the number of his opponent’s pieces that were attacking a given
square, which suggests remarkable availability of many different types of in-
formation about the presented chess position. Ericsson and Oliver (Ericsson &
Staszewski, 1989) found evidence for rapid and flexible retrieval using a retrieval
structure. This research raises the possibility that acquisition of expert-level
chess skill involves the development of skilled memory for chess positions.
Once it is accepted that mediating mechanisms are acquired, that raises a
number of challenging issues. One can no longer assume that superior perfor-
mance is automatically achieved merely as a function of practice. The history of
expert memory performance provides a number of cases in which individuals
who have had extensive practice and experience have settled for suboptimal
methods. Crutcher and Ericsson (Ericsson & Polson, 1988b) found that several
waiters and waitresses who on a daily basis memorized dinner orders relied
on less effective encoding methods than did the expert waiter JC, who exhibited
vastly superior performance. Chase and Eriesson (1981, 1982) documented
Prospects and Limits of the Empirical Study of Expertise 543