The vergence-accommodation conflict, excessive screen disparity, binocular distortions and the motion component in stereoscopic videos are considered as main factors that may induce visual discomfort. In our previous study which was based on the experts-only experiment, we also found that the large relative disparity between the foreground and background and the fast planar motion were more likely to induce visual discomfort. In this study, we conducted the same subjective experiment but on non-expert observers. The subjective experiment results coincided with our previous findings. The two objective visual discomfort models developed in our previous study have been evaluated and showed high correlation with subjective data. Finally, we found that the observers could be classified into different clusters according to their visual discomfort sensitivity to the velocity or the relative disparity. For some observers, the velocity is the predominant factor that may induce visual discomfort; some consider that the relative disparity is the key factor, and some are sensitive to both the velocity and relative disparity.