We report on the infrared spectra of RNiO₃ (R = E, Ho, Y). They provide evidence of phonon and insulating gap behavior and point to the monoclinic distortion at the metal-insulator (MI) transition as a feature for all RNiO₃ (R ≠ La). We hypothesize that the intermediate paramagnetic phase (above TN and below TMI in RNiO₃ (R = Sm, Eu, Ho, Y) might be consequence of a self-doping effect, gradually triggering a phase segregation in electron-rich and electron-poor regions. This picture is concomitant to the temperature-dependent effect of octahedral tilting and distortion and self-trapped electrons in a polaronic medium.