  Cognitive acoustic cues have an important role in shaping the phonological
structure of language as a means to optimal communication. In this paper we
introduced P-trac procedure in order to track dispersion of contrasts in
different contexts in lexicon. The results of applying P-trac procedure to the
case of dispersion of contrasts in pre- consonantal contexts and in consonantal
positions of CVCC sequences in Persian provide Evidence in favor of phonetic
basis of dispersion argued by Licensing by Cue hypothesis and the Dispersion
Theory of Contrast. The P- trac procedure is proved to be very effective in
revealing the dispersion of contrasts in lexicon especially when comparing the
dispersion of contrasts in different contexts.
