It is well known now that speech chain is not constituted by discrete units. Speech sounds have an influence on other sounds directly in contact with them. We hypothesize that this influence is not noise but plays an important role for perception. An experiment is managed to evaluate the relative importance of two kinds of cues: those of phonetic distinctive features (voiced and unvoiced) and those of voicing assimilation (for liquids). Our results confirm that voicing assimilation of liquids plays an important role to identifie clusters: a/ the absence of assimilation cues increases reaction times; b/ subjects use assimilation cues in preference to distinctive features.