  We investigate the effects of suppression of single-particle dispersion near
the Fermi level on the spin gap and the singlet-pairing correlation by using
the exact diagonalization method for finite-size systems. We consider strongly
correlated one-dimensional models, which have flat band dispersions near wave
number k=\pi/2, if the interactions are switched off. Our results for strongly
correlated models show that the spin gap region expands as the single-particle
dispersion becomes flatter. The region where the singlet-pairing correlation is
the most dominant also expands in models with flatter band dispersions. Based
on our numerical results, we propose a pairing mechanism induced by the
flat-band dispersion.
