Intentional binding: an unintentional artifact?
The sense of agency (SoA) is a fundamental aspect of the human experience. Intentional Binding (IB), the subjective compression of the time interval between a voluntary action and its associated outcome, has been proposed as an implicit measure of SoA. Given the fundamental nature of SoA, one would expect the presence of IB in all healthy individuals. To date, empirical investigations of IB have only reported aggregate data averaged across individuals and may inappropriately use parametric statistics on non-normally distributed data. We compared aggregate vs. individual data in a study (N=35) using a variation on the standard IB paradigm. Aggregate results replicated the expected effect of action binding (F(1, 28) = 4.44, p = 0.044) and outcome binding (F (1, 35) = 49.12, p<0.001). Crucially, however, inter-individual analyses revealed that more than half of participants’ mean binding values for either action or outcome (N=20) were in the opposite of the expected direction, in line with results from involuntary action conditions in the literature. Moreover, reanalysis of a publicly available dataset shows a similar pattern; the authors reported a replication of the standard IB effect at the aggregate level but our re-analysis at the individual level revealed 19 out of 20 participants in certain sub-conditions had mean action or outcome binding values in the opposite of the expected direction. These findings indicate the IB phenomenon may be another classic example of how averaging can be misleading and will have important implications for the future of research in this domain.