Timing of the intention to act reflects action feedback expectancy

There is ongoing debate concerning the neurocognitive basis of intention; in particular, whether it is based on predictive or postdictive processes. We addressed this by manipulating the uncertainty of receiving haptic feedback with an action. The perceived time of intention (known as 'W' judgements) was measured using the Libet clock method. In Experiment 1 (N = 36 adults), haptic feedback was either 100% present or absent, or random (50%). W was delayed under conditions of uncertainty (50%), irrespective of the presence or absence of feedback. In Experiment 2 (N = 36 adults), we directly assessed the importance of uncertainty by manipulating the probability of haptic feedback in three conditions: 100%, 75% and 25%. W was delayed in a linear fashion as the probability of receiving haptic feedback decreased. These findings suggest that the reported time of intention is partly informed by the expectancy of action-related sensory feedback.