Intentional Binding in Automated Control Settings Figure 4. Modulation of interval estimates by actual interval between action and effect for each automation level. Stars represent significant effects (p,.01). doi:10.1371/journal.pone.0034075.g004 was automated, or the less it relied on participant’s actual control, the longer the action-effect interval was perceived (all ps,.01). These results indicate that IB is sensitive to levels of automation, with increasing automation leading to a higher interval estimates, which we interpret as a gradual decrease in sense of agency. Finally, the effect of Automation Level was modulated by the Action/Effect delay, as demonstrated by the significant two-way interaction between these factors: F(6,72) = 8.457; p,.01, gp2 = .42. Post-hoc analysis reveals that interval estimates from the medium and large Action/Effect delays were strongly modulated by the automation level (p,.01), whilst estimates from the small Action/effect delays were not significantly modulated (p..01) (see Fig. 4). Explicit Judgement of Agency Each participant returned one judgment of agency per Automation Level (see Fig. 5). A repeated measures ANOVA showed a significant influence of Automation Level, F(3,36) = 46,204; p,.01, gp2 = .79. Post hoc analysis shows that judgement of causality decreased monotonically with the level of automation (all ps,.01). As expected, explicit judgements of agency follow the facts of agency. But this is not completely trivial, as judgements of agency frequently do not follow actual control in situations where agency is ambiguous [19], [20]. Finally, we correlated the mean binding effect and the explicit judgement of agency across the four levels of automation for each individual subject. We then tested the resulting r(3) correlation coefficients for the group of all 13 subjects against 0. Correlation between authorship and binding effects was negative and significant (Mean r = 20.84, SD = 0.105, t(12) = 228.821, p,.001), indicating that as actual levels of control were varied, changes in intentional binding closely tracked explicit judgements of agency. This finding boosts the use of intentional binding as an implicit window into human agency. Discussion In this experiment, we explored intentional binding in a rich and complex situation involving flying an aircraft with various degrees of autopilot assistance. Our study yielded three important results. First, we observed a strong relation between measures of IB and different levels of system automation. Second, our data revealed a gradual increase in temporal estimation with the increasing level of automation. The more the system was automated, the longer the action-effect interval was perceived. Third, the effect of automation level on intentional binding was dependent on the actual action-effect delays. There was a strong effect of automation level on binding for medium and large action- effect intervals and no effect for small action-effect intervals. Such findings have important implications concerning the precise conditions under which the intentional binding effect occurs: intentional binding is an empirically robust phenomenon that occurs in complex control situations, is sensitive to graded variations in actual level of control, and is task dependent. We now discuss these in turn. Robustness of the binding effect Our findings confirm the interest of the intentional binding as implicit measure of agency. First, we provide evidence that quantitative changes in binding are strongly associated with progressive changes in actual level of control, and also with quantitative changes in explicit ratings of agency (but see [9]). Second, we replicate the basic binding effect in a situation with high face-validity, in which action-event sequences paralleled those that participants might meet in their everyday lives. Interactions with machines regularly involve sending a com- mand to a system, and monitoring the system response, and we regularly feel a sense of controlling how the machine behaves in such situations. Our data thus lend external validity to intentional binding. They confirm that temporal distortions associated with agency occur in everyday life. Intentional PLoS ONE | www.plosone.org 4 March 2012 | Volume 7 | Issue 3 | e34075