Short anser is no. In Lightwave and other programs you can specify wether a light affects specular only or diffuse only, or both. This can be handy at times, allowing you to have a fill light that does just that and doesnt create hot specular highlights. Sometimes you want an object to have "false or extra" highlights, in Carrara you are also going to get increased diffuse shading. In Carrara every light affects both specularity and diffuse shading. Hopefully this is something that could be added in the future, as I have relied on it more than a few times in Lightwave.