The effect of response complexity on the lateralized readiness potential

Hackley and Miller (1995) reported that complex sequences of finger movemen ts are preceded by larger LRP amplitudes than simple finger flexions. The p resent study seeks to assess this LRP enhancement in more detail. Experimen t 1 included two further conditions requiring either repeated movements wit h one and the same finger or simultaneous movements with three fingers. Alt hough a clear foreperiod LRP was obtained, its amplitude was insensitive to the movement conditions. Therefore, Experiment 2 assessed whether effects of movement complexity depend on the precision of the required movement. Ho wever, we observed larger LRP amplitudes to complex than to simple movement s under both stringent and lenient response conditions, ruling out an expla nation in terms of required movement precision. Possible explanations for t he inconsistency of the complexity effects on the foreperiod LRP are discus sed.