DISCUSSION
respiratory sinus arrhythmia, Laborde et al., This novel study, anxiety, autonomous nervous systems
DILATION, CONTRACTION
The present study investigated whether a learning environment with a background TV, classical music, or just silence may affect students' ANS activity represented by HR, HRV, BVA, and SCL during and after an experimental academic examination. We found that HR, BVA, and SCL differed significantly among the experimental conditions in all groups. In contrast, HRV time‐domain parameters showed significant differences in the group with the background TV. This group had to process more cognitive information such as audio, audiovisual stimuli, and verbal content. However, HRV parameters remained relatively stable in the groups that listened to classical music or experienced silence. The data partially supported our hypothesis concerning differences in changes in psychophysiological parameters during academic examination. Thus, differences in HR and HRV were more remarkable in the background TV group only during the anticipation period.In previous studies, researchers focused primarily on whether a learning environment with a background TV might influence homework performance or achievement (Pool et al., 2000, The results also demonstrated a decrease in BVA, which reflects arterial dilation and contraction that are controlled by autonomous nervous systems (Lin et al., Another critical issue that we want to highlight is the progression of HRV responses to background TV intervention. As illustrated in Figure In contrast to the HRV decrement observed as a result of the within‐subject comparisons in the background TV group, HRV time‐ and frequency‐domain indices remained almost stable in the background classical music and silence group. These results provided preliminary support for the view that the HRV decrement observed in the background TV group was due to individuals' efforts devoted to filtering out the irrelevant stimulus generated by the TV. It is important to note that the results showed a remarkable vagal withdrawal in the group with background TV. These results could be attributed to the presence of verbal stimuli, which were absent in the groups listening to classical music and experienced silence. Hence, the lyrics of musical pieces might influence how music affects psychophysiological activity during a demanding mental task.As stated earlier in this paper, individuals may believe that listening to classical music while studying lessons may benefit a better learning outcome. However, functional MR and PET studies showed that brain regions associated with the control of attention, memory, working memory, emotion, and the limbic system also engage in processing musical auditory information (Salimpoor et al., Contrary to HRV parameters, HR, and SCL increased and BVA decreased significantly during anticipation and challenge periods in the classical music and silence groups, which means that sympathetic activity has been promoted by our intervention. These results indicated that HRV might be influenced by the severe audiovisual stimulus in contrast to HR, BVA, and SCL. Taken together, based on the results of the present study, especially the decrement in RMSSD and Log HF, we concluded that background TV is a severe stressor that can alter autonomic activity. Moreover, the current study results supported the view that HRV is a valid indicator of psychological and environmental stress, emotional states, and mental challenge (Appelhans & Luecken, The last finding we want to discuss is the relatively stable progress of the LF/HF ratio in all experimental groups. Although our results, in general, indicated a parasympathetic withdrawal and sympathetic elevation, LF/HF ratio which is accepted as sympathovagal balance indice (Laborde et al., This novel study may have some implications for both practitioners and researchers. First, future researchers aiming to understand the effect of background distracting audio and audiovisual stimulus on ANS activity should consider the possibility that HR, HRV, BVA, and SCL are not equally sensitive to distracting stimuli during a demanding mental task. Therefore, we recommend recording several standard psychophysiological biomarkers for a better understanding of the issue. Further, considering the possibility that different participants might tend to respond to stress by activating different major physiological systems (Lacey, The present study has some limitations. In the present study, we did not measure perceived stress in addition to objectively measured stress. Also, we did not measure participants’ perceived state anxiety and difficulty concerning the task. Our study focused solely on the influence of classical music without lyrics in the background. However, previous research indicates that the effect of background music may vary depending on whether it includes lyrics. Therefore, future studies should explore the effects of background music with and without lyrics. Finally, in this study, respiration activity was not monitored and controlled. So, given that the breathing pattern may affect HRV, especially HF power (due to respiratory sinus arrhythmia) (Quintana & Heathers, 