We address the problem of how to differentiate between phonetically-caused aspects of prosody . those that arise from purely physical phonetic factors and are not reflected in the mental lexicon - vs. phonologically-maintained aspects - those that have a psychological component, i.e., arise from the representation in the mental lexicon. Two case studies are reported: the first focusing on the F0 perturbation caused by pre-vocalic voiced and voiceless consonants, and the second, F0 declination in utterances. Differentiating between these two distinct sources of contextual variation may involve testing the influence of posited phonetic causes one-by-one.