Figure 5

Schematic illustration of the experimental mixed design. Participants were asked to fixate on a grey cross constantly displayed on the center of a black screen. Small extensions of the fixation cross (from a visual angle of 0.69° to 0.74°) were presented for 80 ms duration. The extended fixation crosses were unpredictable in their occurrence using a variable SOA of 5–15 s. Additionally, participants pressed a button approximately every 6.5 s (range 5–8 s). With a probability of 50% button presses were followed by a sound immediately (MA, black). In the remaining 50% button presses were not followed by any sound (M, grey). It was not predictable if the button press would initiate a sound or not. Additionally, externally-produced sounds (with the same physical parameters as the self-initiated ones) occurred randomly between button presses (A, blue). Externally-produced sounds were unpredictable in their occurrence with a variable SOA between 5–8 s (mean of 6.5 s).