Figure 1

Sequence of events appearing on each trial in the modified version of ANT experiment. Part A shows the actual sequence of events during the ANT task in our study. Part B shows examples of the target display in the congruent and incongruent condition. Stimuli: The stimulus used for the orienting signal was an asterisk presented at the same location as the target (2.9° of visual angle above or below the fixation point). For the alerting signal, a 2000 Hz and 50 ms sound was used. Lastly, the target display was made up by a target arrow that could point either to the left or to the right and four flankers that could be just plain black lines or arrows pointing either left or right. The length of the arrows was 0.55° and they were 0.06° away from each other. Description of the task: In half of the trials, 50 ms before the target an auditory alerting signal was presented (fig1). After a 400 inter-stimulus-interval (ISI), an orienting cue was presented on 2/3 of the trials above or below the fixation point for 50 ms. After another 50 ms ISI the target and flankers were presented either at the same or the opposite location than the previous orienting signal for 1700 ms, or until the participant gave a response. Then the fixation point that had been presented during the whole trial was kept for a variable duration dependent on the duration of the initial fixation point and on the reaction time of the subject so that every trial was same duration (4050 ms). No screen was presented between trials. Consequently, participants did not know when a trial had finished and the next one was to begin providing uncertainty about the appearance of the signals and increasing their informative value.