The properties of Pr0.7Ca0.3MnO3 resistance random access memory devices have been studied in terms of electrical pulse width, pulse polarity, film thickness, resistivity distribution, temperature dependence, device impedance, and dynamics property. Based on the experimental data it is concluded that the resistance increase is due to localization of valence electrons. Voltage pulse induced high density of excessive nonequilibrium electrons near the cathode of the device caused the free valence electrons in transition metal oxide to be localized, the well known Jahn-Teller effect. The voltage pulse induced reduction of resistance is due to delocalization of localized valence electrons by high electric fields.