This paper presents the results of a set of perception experiments concerning the phonological status of early, medial and late F0 peak synchronization in English and the nature of the contrast between these categories. By means of one identification and two discrimination tasks, it has been shown that subjects perceive a categorical-like change when the F0 maximum of a peak is shifted into the stressed vowel and a gradual change when the F0 maximum is moved into the following unstressed vowel. Therefore, we conclude that the early peak constitutes a phonological category as opposed to medial peaks; late peaks form a phonetic continuum.