This paper presents 3 experiments in which the detection of initial vowel monitoring was performed on words preceded by critical words containing a phoneme similar to the target. Results show that in this case, the detection time of the target is increased. But we observe that this "interference effect" only emerges when the two words appear in the same prosodic group. This suggests that the interference effect seems to be sensitive to prosodic information. Thus, it could be tool to investigate the area of prosodic segmentation of speech. Key-words: Psycholingui sties, Speech Segmentation, Prosody.