Fig. 1.

Experiment block design. A total of five active blocks existed for each of the (a) control and (b) stress condition. In each block, arithmetic tasks produced for thirty second followed by twenty second rest. During the 30 s task, several arithmetic questions would be posted depend on how fast the respond of the participant in answering each question. If the respond rate is 2 s per question, the total number of questions per block would be 15 questions and the total number of questions would be 75 questions, for example. During the 20 s rest, the computer screen would display with a fixation cross with black background and participants were instructed to look at the fixation cross as a visual cue for trial onset. The red dashed-line marks the start of the task and the green dashed-line marks the end of the task (the marker was presented in every block). The stressors were based on time pressure and negative feedback of individual performance as demonstrated in (b). Five samples (S1-S5) of alpha amylase were collected; 5-minutes before the control condition as baseline for control, immediately after control condition, 5-minutes before stress condition, immediately after stress condition and 5-minutes after stress condition as marked in the figure with yellow rectangular.