  Line profiles can provide fundamental information on the physics of active
galactic nuclei (AGN). In the case of narrow-line Seyfert 1 galaxies (NLS1s)
this is of particular importance since past studies revealed how their
permitted line profiles are well reproduced by a Lorentzian function instead of
a Gaussian. This has been explained with different properties of the broad-line
region (BLR), which may present a more pronounced turbulent motions in NLS1s
with respect to other AGN. We investigated the line profiles in a recent large
NLS1 sample classified using SDSS, and we divided the sources into two
subsamples according to their line shapes, Gaussian or Lorentzian. The line
profiles clearly separate all the properties of NLS1s. Black hole mass,
Eddington ratio, [O III], and Fe II strength are all very different in the
Lorentzian and Gaussian samples. We interpret this in terms of evolution within
the class of NLS1s. The Lorentzian sources may be the youngest objects, while
Gaussian profiles may be typically associated to more evolved objects. Further
detailed spectroscopic studies are needed to fully confirm our hypothesis.
