Quantum molecular dynamics simulations have been carried out to calculate the diffusion coefficients and the activation energies of protonic defects in BaCeO3, BaZrO3, SrTiO3 and CaTiO3. The calculated activation energies are in agreement with experimental data within statistical uncertainty. The activation energy for proton transfer is found to be significantly affected by the repulsive interaction of the proton with the B-cation (B=Ce, Zr, Ti). A physical interpretation for the measured infra-red spectra can also be obtained From the numerical results.