Mental Arithmetic Protocol for Cognitive Load Measurement

The mental arithmetic task was designed to cause mental workload (MWL) based on previous studies (So et al., 2017 (link); Jost et al., 2019 (link)) and was divided into two task levels: low- and high-MWL. The low-MWL task consisted of easy questions involving single-digit addition and subtraction (i.e., 3+2, 4–1, with numbers ranging from 1 to 9). The high-MWL task consisted of difficult questions involving mixed arithmetic operations (i.e., 36×7–24, 43+72/9, number range 1–99). The mental arithmetic task questions were randomly presented within a defined range, and included a true answer result and two false confusion results. The two false results were automatically calculated by randomly adding or subtracting a number in the range of 1–5 from the correct answer. Participants were required to select the correct answer using the arrow and spacebar keys of the keyboard, as shown in Figure 1. ERP and mental arithmetic tasks were developed using LabVIEW2016 (National Instruments Inc., Austin, TX, United States).