Fixation duration can be used to indicate cognitive load and the depth of processing (Kruger & Doherty, 2016; Jacob & Karn, 2003; Krejtz, Duchowski, Krejtz, Kopacz, & Chrzastowski-Wachtel, 2016; Liu & Chuang, 2011; Chen, Hsiao, She, 2015; Schüler, Scheiter, & Gerjets, 2012; Yang, Chang, Chien, Chien, & Tseng, 2013; Kickmeier-Rust, Hillemann, & Albert, 2011)