Materials and stimuli
Apparatus. E-prime version 2.0.10.242 software (Psychology Software Tools, Pittsburgh, PA) was used. The computer model was Dell Inspiron 22- 3264 with Window 10 operation system installed. The display resolution of screen was 1024 × 768. Emotional facial stimuli are presented at a distance of approximate 45 cm with a resolution of 210 × 240 for each emotional face.
Cognitive load. The distraction involved mathematical equations with addition and subtraction as cognitive load. There were 36 trials of mathematical equations in each level of distraction, 108 trials in total. The varying levels of complexity of mathematical equations implicated that the amount of cognitive load was actively maintained in WM. Three levels of distraction were resulted: control, low, and high. Cognitive load was operationalized as a function of distraction in which a given event captures WM resources thus hindering other central activities. The low level of distraction indicated lower cognitive load; the high level of distraction indicated higher cognitive load.
To experimentally varied the three levels of distraction, the operand in each equation increased (e.g., 1+9=8 or 9-7=6 in the control level; 19+1=20 in the low level; 10+2-1=5 in the high level). The processing component was performed progressively, namely the control level of distraction was performed firstly, and then the low level following the high level.
As the relatively increasing complexity of mathematical equations in the subsequent levels, their average time used in the processing component in the control level (plus 3 SD ) was then used for the subsequent processing component for the corresponding individual.
The emotional faces. All emotional facial stimuli were obtained from Yale face database (Georghiades, 1997). Facial stimuli of 15 individuals included positive, negative, and neutral faces. All facial stimuli are grey-scaled images. Originally, participants were required to solve mathematical equations while remembering letters in Aospan. Major modification that changed to-be-remember letters to naturally emotional faces was made to Aospan. A block design was used, with each block contained 36 trials of mathematical equations and 36 trials of emotional faces. Each level of distraction consisted of 3 blocks for each type of emotional faces. Except for the control level, it contained 4 blocks with one of those blocks used for 36 mathematical equations to calculate the time limit for differences in individual ability. The accuracy criterion was 85% which prevented participants from answering these by chance. Three of the remaining blocks in the control level comprised 12 trials of each type of emotional faces.