Empirical studies having addressed the free-will issue suffer from controversial methodologies and interpretations. We present a new paradigm involving a synchronization task where the time interval to synchronize with is randomly within and without subject's synchronization capabilities and ask subjects to retrospectively evaluate (Q1) which of the two occurred or (Q2) whether their motor response had had been reactive/speeded or delayed. Contrary to the non-FW view, Q1-judgments correlate with the actual duration of the synchronization interval rather than with subjects's motor response latencies. Instead of postidictively reshuffling their judgment to make it match the outcome of their actions, subjects preserve the causal chain of events having entailed them. When answering Q2 subjects' judgments also correlate with the synchronization interval, proof that they cannot decide on the intentionality of their actions. Hence the present results reveal the intrinsic duality of the free-will concept
