Optical heterodyne detected optical Kerr effect (OHD-OKE) experiments are used to study the orientational dynamics of the liquid crystal 4'-octyl-4-biphenylcarbonitrile (8CB) in the isotropic phase near the isotropic to nematic phase transition. The results are compared to those for three other liquid crystals. The 8CB data display a short time scale temperature independent power law decay and a long time scale exponential decay with a temperature dependence described by Landau-de Gennes theory. The power law exponent is -0.56. Combining this result with previous results for three other liquid crystals [J. Chem. Phys. 116 (2002) 6339; J. Chem. Phys. 116 (2002) 3601, it is found that the power law exponent depends linearly on the aspect ratio of the liquid crystal. (C) 2002 Elsevier Science B.V. All rights reserved.