Choice of priors in estimation

Dear all.

Before starting the search for the posterior mode in estimation Dynare shows the initial value of the log posterior (or the objective function).
Two questions:

  1. Is this initial objective function value computed at the mean of the assumed parameter prior distributions?

  2. If yes, is it correct to claim that a set of prior distributions that produces a higher initial objective function value will also produce a higher posterior marginal data density (e.g. higher Modfied Harmonic Mean value) and that therefore this is a good way for one to choose the priors?

Thanks a lot a regard!