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to be repeated in 44% of all trials. All analyses were conducted separately for the trials with and without a repetition of the second fixation check and there were no systematic differences. Thus for the analyses in this article we used fixations from all trials. 

## Data Analysis 

Data preprocessing and saccade detection . For saccade detection we applied a velocity- based algorithm (Engbert & Kliegl, 2003; Engbert & Mergenthaler, 2006). Saccades had a minimum amplitude of 0 . 58 ◦ and exceeded the average velocity during a trial by 6 standard (median-based) deviations for at least 6 data samples (6 ms). The epoch between two subsequent saccades was defined as a fixation. The number of fixations for further analyses was 47 330. 

