No other pairwise t-test was significant, suggesting that the observed main effect of "trial type" was predominantly driven by the difference between "action only" trials and "action + tone" trials in the "variable outcome timing" block.
Compared to "action only" trials in "variable outcome timing" blocks, subjective action time in "action + tone" trials for which the action – outcome delay was 50 ms or 450 ms did not show the shift towards the outcome observed for the action – outcome delay of 250 ms.
Following previous studies on binding of subjective action time (Haggard et al., 2002), we subtracted the mean time judgement error in "baseline" blocks from mean time judgement errors in "variable outcome timing" and "fixed outcome timing" blocks for each participant.
It accommodates a pool of independently-clocked timers and counters, organised in timing blocks, and, consequently, is able to support, in parallel, traffic streams with diverse timing requirements.
There were three "fixed outcome timing" blocks and three "variable outcome timing" blocks, presented consecutively, with the order of the two conditions fully counterbalanced across subjects.
Tones followed the button presses either after a fixed delay of 250 ms (in "fixed outcome timing" blocks) or after a variable delay of either 50 ms, 250 ms or 450 ms (with equal probabilities) (in "variable outcome timing" blocks).
For completeness, we report the shifts observed for "action + tone" trials in "variable outcome timing" blocks in which the action – outcome delay (and, therefore, bottom-up drive) differed from "fixed outcome timing" blocks.
75% of trials in "variable outcome timing" and "fixed outcome timing" blocks were "action + tone" trials, in which participants' button presses were followed by one of two sine wave tones (750 Hz or 800 Hz, 100 ms duration).
Therefore, we first focused on "action + tone" trials with identical trial event timing in both "variable" and "fixed" outcome timing blocks, i.e., on trials with an action – outcome delay of 250 ms.
In addition, we report results for "action + tone" trials in "variable outcome timing" blocks that were based on the two alternative action – outcome delays separately (50 ms and 450 ms).
