Rudy Marinacci recently wrote:
“I enjoyed your ‘How is a Hippo like a Feather‘ article and chart very much. Could you tell me why my mother and her brother, both from Southern Italy (Reggio Calabria) could not pronounce ‘th’ and said tin iunstead of thin and tick, not thick?”
Sure can. It is because [th] is more difficult to pronounce than other English linguistic sounds. It is an “interdental” sound, which means the tongue goes between the teeth to pronounce it. It is relatively more difficult to get your tongue in between your teeth and out again before the following vowel.
The pronunciation of [t] is not that far away. It is a dental, which means the tongue goes to just behind the upper teeth to pronounce it. Much easier. The tongue remains where it is in pronouncing all other linguistic sounds (phonemes): behind the teeth. This is why people from Brooklyn, Queens, and the Deep South make the same sound change.
There is another problem your mother faces: she gets no help from Italian. This is because there simply is no [th] in Italian. In fact, this sound does not appear in any Romance languages. (Diego is right about the difference between English [th] and the Spanish dental fricative.)
Don’t worry about your mother’s pronunciation. As I said above, people from Brooklyn, Queens, and throughout the rural regions of the South (where I come from) face the same problem. She is in the company of native speakers of English around the world.