1 of 8 digit-digit coding tasks varying in 2 levels of stimulus uncertainty (U-sub(s)) and 4 levels of S-R compatibility were administered to 8 different groups of 10 Ss each. Response speed was found to vary as a function of S-R compatibility and this effect increased as U-sub(s) was raised from 1 to 3 bits. S-R compatibility effects in these tasks, in which sets of stimuli were identical and mode of motor response was held constant, were ascribed to the availability of logical S-R translation rules as a function of preexperimental experience. (PsycINFO Database Record (c) 2006 APA, all rights reserved)