Effects of different acquisition procedures on response variability

In three experiments with college students, the effects of different acquisition procedures on response variability were studied. The computer keypressing task involved learning a sequence with a minimum number of presses on a subset of the keyboard. Procedures differed in type of training and in the number, size, and sequence of training steps. Experiment 1 showed that instructions and shaping in three steps generated less variability in the number of responses made in each keypress sequence than shaping in six steps. Subsequent experiments showed that a large increase in the response requirement early in shaping increased variability. Postacquisition variability remained unchanged in the number of responses per sequence—the aspect of responding on which reinforcement was contingent—but declined in location and timing of keypressing. The results are discussed in terms of the implicit reinforcement of variability and how the acquisition of qualitatively different response strategies could influence variability.