Effects of Constant and Incremental Modes of Music Volume and Odor Concentration on Vigilance

A within-subjects design was adopted, in which 26 participants completed the Psychomotor Vigilance Task (PVT) under five experimental conditions. Subjective vigilance ratings (Karolinska Sleepiness Scale, KSS), behavioral performance indicators (reaction time and number of lapses), and physiological indicators (high-frequency heart rate variability, HF) were collected simultaneously.

The results showed that, compared with the no-stimulus control condition, any condition containing either music or odor stimulation significantly enhanced vigilance. Further analysis revealed that, for both the auditory and olfactory channels, the incremental mode was more effective than the constant mode in maintaining the vigilance state during the task. When both music and odor were presented in the incremental mode, a significant synergistic enhancement effect emerged; participants demonstrated optimal performance in subjective vigilance, reaction speed, number of lapses, and HF values.