Do the same stimulus-response relations influence choice reactions initially and after practice?

A two-choice reaction task was used to evaluate changes in stimulus-response translation with practice. In Experiment 1, four groups of Ss practiced with either a direct or indirect mapping of left-right stimuli to left-right responses and either a crossed or uncrossed hand placement and transferred to one of the four Mapping x Placement conditions. Stimulus-response location and response location-effector relations affected performance initially and after practice. In Experiments 2 and 3, Ss switched every 42 trials between conditions for which only the stimulus location-effector (Experiment 2) or stimulus-response location relation (Experiment 3) remained constant. Switching produced interference in Experiment 2 but not in Experiment 3, corroborating the influence of the stimulus-response location relation on performance. Mediation based on spatial codes continues to be a factor in the performance of practiced Ss.