Partial advance information and response preparation: inferences from the lateralized readiness potential.

Response speed to a signal is faster when advance information about the forthcoming movement is provided before signal onset. Although this precuing effect is well established, the location of this saving in reaction time (RT) in the information-processing system is controversial. Some authors have claimed that the precuing effect resides at a motoric level, whereas others have suggested a nonmotoric locus. The present experiments used onset latencies of the lateralized readiness potential (LRP) to locate the precuing effect. The results of 2 experiments with a highly compatible (Experiment 1) and with an incompatible (Experiment 2) stimulus-response mapping indicate that this effect resides, at least partially, in the motoric portion of RT. In addition, the LRP amplitude before signal appearance increased with the amount of advance information, supporting a muscle-specific preparation hypothesis.