The electronic structures, Born effective charges (BEC), and interatomic force constants of BaMO3 (M = Ti, Zr, Hf, Sn) in the cubic perovskite structure are computed using first-principles density functional theory. Comparison with the Maximally-localized Wannier function description of the electronic structures for BaTiO3 shows that the change of a single constituent (Ti to Zr, Hf, and Sn) has pronounce effects on the orbital hybridizations with the oxygen, with significant implications for the nature of the BEC anomalous of the compounds. Examination of the real-space interatomic force constants shows that the key interatomic interactions are strongly dependent on the constituent's dynamical effective charge and the very delicate compensation between the short-range interactions and long-range dipole-dipole interactions gives rise to the ferroelectric structural instabilities.