Data recording and analysis procedures were the same BTK inhibitor as those used in the affordance experiment. Left- and right-pointing double arrowheads (e.g., “<<” and “>>”) served as primes and targets. The lines making up these stimuli were each 1 degree of visual angle long, and the lines in each arrowhead had an angular separation of 60° (30° above and below the horizontal). Masks were constructed of 30 pseudo-randomly orientated lines arranged into a 6 × 5 grid centred over the centre of the screen. To

prevent any perceptual interactions between prime and mask modulating priming effects (see “object updating” accounts of the NCE e.g., Lleras and Enns, 2004) lines in the mask avoided any orientation within 5 degrees of the lines making up the prime and target. The lines in the mask were between 1.5 and 3 degrees of visual angle long. Line length and orientation were determined randomly within these limits and independently for each line in the mask. Thus, the mask was between 3.5 × 3.5–5.5 × 5.5 degrees

of visual angle, centred on the centre of the screen. A new mask was constructed on each trial to prevent perceptual CHIR-99021 ic50 learning of the mask which could in turn lead to increased prime identification (e.g., Schlaghecken et al., 2008). Such masks have been shown not to invoke NCEs by object updating (Sumner, 2008) or by perceptual interactions (Boy and Sumner, 2010), and thus any NCEs observed can be attributed to motor inhibition. Prior to the main experiment, the duration of the prime was set to below the threshold for conscious perception (50 msec duration) using a psychophysical staircase procedure. Here, on each trial a prime and mask were presented with Suplatast tosilate no target, and the participant was instructed to make a 2-alternative forced-choice button-press

according to the direction of the prime stimulus. The participant was instructed to make their best guess if they were unsure of prime direction, to concentrate on being accurate, and that speed was unimportant for this part of the task. The prime duration began at 120 msec, and then was varied according to a fixed-step, 1-up/2-down procedure: After two consecutive correct responses to primes presented at the same duration, prime duration was reduced by 10 msec on the next trial; after an incorrect response it was increased by 10 msec, within a range of 10–200 msec. This staircase procedure terminated after 10 “reversals”. The fastest prime duration was 60 msec (which was presented twice, and the prime was incorrectly identified on the second presentation), and the mean prime duration at the reversals was 84 msec. Thus, for the remainder of the experiment the prime duration was set to 50 msec, which was the faster than the fastest prime duration measured during the staircase (and was not reliably identified), and faster than the average duration of the reversals. We followed the method described in Schlaghecken et al.