Extending the Eigenvector 1 Space to the Optical Variability of Quasars

We introduce a new physical parameter, the optical variability amplitude, to the well-established Eigenvector 1 space of quasars and test a sample of long-term B-band light curves of 42 PG quasars monitored by Giveon et al. (1999). We find that the optical variability amplitude strongly correlates with the intensity ratio of Fe II to H$\beta$, H$\beta$ width and peak luminosity at 5007$\rm{\AA}$. We briefly discuss the physical meaning of our findings and suggest that the Eddington ratio may be a key factor in determining a quasar's variability.