Formation of a Mental Abacus for Computation and Its Use as a Memory Device for Digits: A Developmental Study.

In order to examine whether representational changes in digit memory would be observed as a function of the extent of expertise in mental-abacus operation, five groups of operators, differing in extent of expertise (i.e., novices, lower intermediates, intermediates, junior experts, and experts), were required (a) to reproduce series of five digits either forward or backward as quickly as possible and (b) to perform a simple aural-verbal or visual-spatial task interpolated between the presentation and reproduction of a near-span series of digits. The intermediates and more skilled operators as well as a majority of the lower intermediates showed nearly equal amounts of time for forward and backward reproduction, whereas novices took a much longer time for backward than for forward reproduction. The more skilled operators were, the less vulnerable was their memory for digits to the aural-verbal interpolated task (a relation that was significant) and the more vulnerable to the visual-spatial task (a relation that was insignificant). These results strongly suggest that the advanced operators applied their mental abacus to digit memory. It is claimed that a system of representation formed through routine problem solving is transferred automatically to other cognitive tasks.