2.1. Participants
A total of 63 healthy, undergraduates with a mean age of 19.46 years (SD = 1.82, female = 36) were recruited for the present study. All participants were prescreened using the State-Trait Anxiety Inventory (T-AI score >45) and the Beck Depression Inventory (BDI-II score > 15), as well as for abnormal BMI (>28 or <18), regular intake of medicine, use of hormonal contraceptives (current; female participants only), consumption of alcohol or coffee, and existence of chronic or acute illnesses. Two participants were excluded from the final analysis: one quit during the stress induction procedure and another was withdrawn because of computer failure. The final sample comprised 60 individuals (female = 31,M age=19.57, SD = 1.84) who met the inclusion criteria and completed all the tests.
To determine sample size, a statistical power analysis was conducted based on a medium effect size (Cohen’s f = 0.25), which suggested that 54 participants were required in order to detect the hypothesized effect at α= 0.05 and β = 0.95. Participants provided written informed consent and all procedures were conducted following the Declaration of Helsinki. Prior to the experiment, participants were asked not to eat, exercise, or consume caffeine for 2 hours. Randomly chosen groups of participants were allocated to either the stress condition (n = 31) or the control condition (n = 32).
The study pursued the principles of the Declaration of Helsinki (World Medical Association, 2013) and was approved by the Academic Committee of the Ministry of Education of the Key Laboratory of Modern Teaching Technology, Shaanxi Normal University in China. Prior to the experiment, all participants were required to provide written informed consent. And each participant received payment as a token of appreciation for their participation in the study.