CONCLUSION
Results of the present study indicated that classical music and silence gave rise to almost similar responses in terms of recorded psychophysiological biomarkers which means that classical music has at least null effects during a mental task. Rather, a certain type of music especially calm music with no lyrics might speed up tonic vagal activity and increase autonomic regulation capacity in reading comprehension tasks. Students might benefit from Johann Sebastian Bach's classical music composition of Orchestral Suite No. 3 in D major while engaging in a demanding reading comprehension task. We also concluded that the impact of music or other background audio and audiovisual stimuli may be influenced by the presence of verbal contents in those stimuli. In this respect, the background TV having audio, audiovisual stimuli, and more critically verbal content that can interfere with reading tasks might suppress vagal activity. Finally, the HR, HRV, BVA, and SCL methods are not equally sensitive mediums to indexing ANS activity in a learning environment. In this regard, HRV may represent students' sympathetic and parasympathetic activity only when they are exposed to severe stimuli during a cognitive task. Studies executed with SCL and BVA may give more precise results if performed with HRV.