Participants Thirteen participants (4 females; mean age of 32 years) from the french aerospace lab took part. Participants were naive to the purposes of the manipulation, had normal or corrected- to-normal vision and no particular expertise in controlling an aircraft. Materials and apparatus The simulator (see Fig. 1) included a navigation display (22-in screen) including the navigation of the aircraft in the horizontal plane and the surrounding traffic. An adjacent monitor (17-in touch screen) showed an autopilot interface, and allowed the participant to change the aircraft’s horizontal trajectory in case of conflict, such as being too close to another aircraft. Moreover, a scale below the autopilot interface enabled recording of partici- pants’ responses to agency questions (see later). Thus, the autopilot interface allowed the participant to choose and then execute actions, in a manner analogous to the keypresses in a standard agency experiment. The navigation display showed the effect of the executed action as a visual representation of aircraft heading. Design and procedure The participants’ task was to track the progress of their aircraft on a predefined flight path and intervene as the situation required. In particular, when another aircraft appeared on the flight path, the participant had to perform an appropriate command (see later) to change their aircraft’s heading direction using the autopilot interface. The sequence of events on each trial was as follows (see Fig. 2). At the beginning of each trial, participants supervised the navigation of the aircraft on the flight plan. (1) After a randomized short interval, a conflict appeared due to presence of an obstacle (another aircraft) on their path. The participant detected the conflict by a red circle around the obstacle. (2) The participant decided an appropriate heading command, (3) implemented it using a scroll wheel on the interface, and (4) finally executed it by pressing an engagement button. Importantly, the action was effective only after the participant’s engagement of the command. This engagement was marked by the appearance of a green light on the interface coupled to a short sound. (5) After a controlled temporal delay, feedback concerning the success of the action Intentional Binding in Automated Control Settings engaged was sent to the participants: a green message ‘‘resolved’’ plus a sound if successful action; a red message ‘‘not resolved’’ with a different sound if not. (6) After each trial, and whatever the success of the command engaged, participants had to estimate on a scale from 0 s to 3 s the temporal delay perceived between the keypress to engage their command and the appearance of the visual feedback (‘‘conflict resolved’’ or ‘‘conflict not resolved’’). In the Full Automated Control condition (see below), where participants did not make a keypress, they judged the time between the appearance of the green ‘engagement’ light plus accompanying sound and the conflict resolution feedback. They were told that the possible range of delays was between 1 ms and 2999 ms. In fact, only three Action/Effect delays (750 ms, 1500 ms, and 2250 ms) were presented, in a random order. In order to meet the task requirement, participants had automation tools to predict conflicts with the surrounding traffic, alert humans of this conflict, and provide commands or guidance to resolve the conflict. In order to study how level of automation affect the sense of agency, automation level was varied between block of trials. In accordance with an established classification [18], four different levels of automation were tested (see Fig. 3) with, from the least automated condition to the more automated condition: – The Full Operator Control (FOC) condition: conflict detection was automatic; Heading decision, implementation of the decision, and engagement of the adjusted heading command were performed by the participant; – The condition: conflict detection and heading decision were automatic (navigation display indicated a new heading direction which would avoid the conflict); Implementation of the indicated heading using the scroll wheel, and engagement of this decision using the keypress were performed by the participant; – The Automatic decision and implementation - Operator engagement (ADI- OE) condition: conflict detection, heading decision and imple- mentation of this decision were automatic; Engagement of the command was performed by the participant with a keypress; – the Full Automatic control (FAC) condition: Automation tools predicted the conflict, selected, implemented and engaged the Figure 1. Experimental set up with the navigation display on the left, and the autopilot interface on the right. doi:10.1371/journal.pone.0034075.g001 PLoS ONE | www.plosone.org 2 March 2012 | Volume 7 | Issue 3 | e34075