Dynamic light scattering data from highly absorbing solutions exhibit intensity-intensity correlation functions characterized by a sum of exponential decays superposed with an oscillatory term. Anew analytical treatment is proposed, which explains this behavior as arising from the heterodyning of scattered light from two distinct species in convective motion. Similar data were obtained both for solutions of polyaniline (PANI) as well as for a complex of cytochrome c and cytochrome c peroxidase in phosphate buffer. This suggests the generality of the phenomenon for polymers that both absorb light and aggregate, such as proteins and conducting polymers. Effects of laser power on convection, thermal lensing, and coning of the beam and concentration of absorbing species have been considered. The presence or absence of the oscillations is shown to be a sensitive indication of aggregation.