A constraint on progressive consonantal assimilation

Rules of assimilation, one of the most common phonological processes, occur in a large variety of types. However, from examining a large sample of assimilation rules, it is evident that there are many assimilations which one could conceive of but which do not appear to occur. This paper will survey the types of assimilation rules in clusters of true consonants. We propose the following constraint on progressive consonantal assimilations: such assimilation rules do not change the primary place of articulation in clusters of true consonants. Further, we suggest that there is a strong correlation between syllable position and the direction of assimilation which may explain why regressive assimilation is far more common than progressive*