Procedure.
The participants were individually tested in the computer laboratory and informed consent was obtained from all individual participants included in the study. First, they were instructed to enter their information into the start-up information of E-prime, including their age and sex. Then, they were instructed to perform the computerized experiment – the modified Aospan. They were required to complete the practice trials before each condition of the distracting task, and then complete the real trials.
Each practice session contained 3 trials presented in math-emotional face strings. The presentation of processing component (distraction) and storage component (serial recall of emotional faces) in the control level was serial, the practice session in the control condition required them to solve 3 trials of mathematical equations and then 3 trials of emotional faces with a set size of 3 for recalling in the same presented order. In both the practice and real trial, all the emotional faces were presented on the screen for 800 ms. At the recall, the participant saw a 3 × 2 matrix of emotional faces.
In the control level, they first solved 36 real trials of mathematical equations and then performed 12 real trials for each type of emotional faces at the set size of 3. For each of the subsequent trials of the low and high level of distraction, the mathematical equations were paralleled with the emotional faces. In the low level, the participants performed 3 strings; thus, the set size for recalling the emotional faces was 3. In the high level, they performed 6 strings in which the set size for recalling the emotional faces was doubled to 6 as to increase the difficulty. The sequence of the levels of distraction was in fixed order. The order for types of emotional faces was counterbalance between participants and emotional faces for recalling were pseudorandomized. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.