Lost in time...: The search for intentions and Readiness Potentials

In 1983 Libet et al. found that the Readiness Potential (RP) precedes the intention to act by 350 ms and the actual movement by 500 ms on average. Using our own replication study, we illustrate how seemingly innocuous technical details are actually crucially relevant to the debate surrounding the interpretation of Libet-style experiments. For instance, using one specific method for determining the RP onset actually led to a reversal of Libet’s results (i.e., the intention preceded the RP onset) for one of the participants. Claims regarding the causal relation between RP and intention cannot be based on averages, but require individual, case by case analyses, which show no exceptions in the temporal relation between RP and intention. We conclude that, properly speaking, Libet-style results in themselves cannot yet be taken as proof for the type of conclusions that are often formulated regarding the non-existence of free will.