Place:
a) This change typically involves the alveolar consonants /t/, /d/, /n/, /s/, /z/.
b) The alveolar sounds /t, d, n/ are extremely prone to assimilation as their place of articulation is in the middle of the oral cavity. Their place of articulation may move further to the front or further to the back.
c) The alveolar fricatives /s/ and /z/.
The alveolar fricatives /s/ and /z/ assimilate phonemically in only one direction, to the equivalent post-alveolar fricatives /ʃ/ and ʒ/. This is because /s, z, ʃ, ʒ/ are all sibilant sounds, while the remaining fricatives are not.