  We discuss the relation between the Polyakov loop and the chiral order
parameter at finite temperature. For that purpose we analyse an effective model
proposed by Gocksch and Ogilvie, which is constructed by the double expansion
of strong coupling and large dimensionality. We make improvements in dealing
with the model and then obtain plausible results for the behaviours of both the
Polyakov loop and the chiral scalar condensate. The pseudo-critical temperature
read from the Polyakov loop turns out to coincide exactly with that read from
the chiral scalar condensate. Within the model study based on the strong
coupling expansion, the coincidence of the pseudo-critical temperatures results
from the fact that the jump of the Polyakov loop in the presence of dynamical
quarks should signify the chiral phase transition rather than the deconfinement
transition.
