Radio-frequency dielectric dispersion is reported for SrTiO3 and KTaO3:X, where XŠ=ŠNb, Na, Li and zero. For all samples except KTaO3:Li, the dominant dispersion arises from Debye-type relaxation with one well-defined relaxation time of the order of 10-8Šs. These findings are identical with those in prototype ferroelectrics having an order-disorder type transition, e.g., KH2PO4. Li-doping quenches Debye relaxation in favour of a polydispersive audiofrequency relaxation step. Li ions (and to a limited extent, Na ions) impose their random-site disordered dynamics on the polar configuration of KTaO3:X which is reached by a gradual freeze of uncorrelated polar motion. © IOP Publishing Ltd.