This paper presents a psychophysiological analysis using galvanic skin response (GSR) signals recorded during a subjective quality assessment of 360° videos viewed on head-mounted displays (HMDs). During the test, participants provided opinion scores based on their perceived video quality. Participants were grouped by their prior virtual reality (VR) experience level into experts, sometimes used, and never used. Additionally, participants whose ratings deviated significantly from the majority were classified as outliers, and their GSR data were also analyzed. The novelty of this work lies in the comparative analysis of GSR responses across different VR experience levels, including the outliers during subjective quality assessment tests for 360° ' videos. Results show that experts exhibited lower GSR amplitudes and fewer peaks, indicating reduced emotional or cognitive arousal. Conversely, participants with sometimes used and never used showed elevated physiological responses and peaks compared to experts. While the outlier group reported the highest number of peaks, it also showed statistically significant differences between the experts and sometimes used experience levels. These findings suggest that prior VR experience influences subjective quality assessments and that GSR metrics can serve as a valuable indicator for participant screening and refining experimental design in immersive multimedia evaluations.