The electro-optical Kerr effect was studied for mixtures of low molar mass liquid crystals within the isotropic phase in the neighbourhood of the nematic phase. The mixtures are characterized by components having similar or antagonistic dipole configurations, as well as different molecular geometries (calamitic and discotic). The investigations reveal that simple mixing rules can be applied for the description of the Kerr response of the mixtures in spite of the fact that the Kerr response displays a set of unusual features, among them a temperature induced sign inversion and synergistic effects.