Experimental design and stimuli configuration.

<p>Panel A. Trial sequence of Experiments 1–3. Participants were instructed to maintain fixation and to make a saccade towards a square appearing to the right side of the fixation cross at 7.7° of eccentricity as soon as the central dot turned green. Participants reported the orientation of a Gabor patch presented for 30 ms and tilted either clockwise or counterclockwise. In mask trials, patches of white noise were displayed at each refresh rate filling in the placeholders before and after the Gabor presentation. In the current figure, a mask trial is depicted with the flankers all set as vertical, as in Experiments 1 and 2 (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0178902#sec016" target="_blank">2</a> also included a random orientation condition). In Experiment 3 and 4, the flankers were constructed in a way that if the central Gabor was oriented to the left, the average of the orientation of the flankers was oriented to the right (and vice-versa). We manipulated the mean orientation so that it spanned from -20 to +20 degrees. Stimuli are not drawn to scale, but rather to illustrate the configuration.