For a wide range of crystalline and amorphous materials, in the low frequency regime, the a.c. conductivity spectra is described by the well known Jonscher's power law equation. Recently, it has been shown that although the pre-exponential factor of the power law equation A and the power law exponent n are sensitive to the composition of materials, the ratio (log A / n ) does not depend either on the composition or on the temperature. In the present work, in order to verify the universality of such behaviors, the variations of the ratio (log A / n ) with respect to the lithium content, and to the temperature have been studied for La 1/3- x Li 3 x TaO 3 . The results indicate that for both variables, the constancy of the ratio is not universal. By analyzing the composition dependence of the power law exponent based on the dimensionality of lithium ion transport pathways in the material, we have satisfactorily explained the behavior of the ratio (log A / n ).