Manipulating procedural variables in a spatial precuing task.

Spatial precuing tasks have yielded a consistent pattern of differential reaction time benefits. Specifically, precuing of two fingers on the same hand has been shown to result in faster discrete finger responses than precuing of two fingers on different hands. This phenomenon is called the hand advantage. Within the context of the spatial precuing task originally developed by Miller (1982), a series of four experiments investigated the influences of two procedural variables on the hand advantage: preparation instruction and presentation mode of preparation intervals. Two preparation instruction conditions were compared: implicit versus explicit instructions regarding preparation possibilities. Also, two presentation modes of preparation intervals were studied: a random condition, in which the preparation intervals varied randomly, and a blocked condition, in which the preparation intervals were grouped together in blocks of trials. Results showed that these two procedural variables, when manipulated independently, did not affect the hand advantage. However, when combined, they significantly reduced the hand advantage by half. Moreover, both procedural variables were shown to produce a precuing benefit for two homologous fingers on different hands. We concluded that, in spatial precuing tasks, procedural variables play an important role by inducing preparation strategies, which affect the pattern of reaction time benefits.