While learning to speak their first language, young children make predictable pronunciation "errors" which generally have no significant negative impact on their ability to be understood by adults. These "errors" are called phonological processes, and they occur in every spoken language.
Sometimes a child may use, outgrow, and then re-employ the same phonological process at multiple stages in acquiring a given language. The order in which phonological processes occur, are outgrown, reoccur, and are again outgrown, is predictable within each discrete language, and two different languages will have different phonological processes occurring in different orders. This is because each language uses its own unique sound system, requiring children of that language to learn to identify and produce a unique set of sounds. The sounds of Welsh differ from the sounds of English or Spanish, and so children learning Welsh will make different errors from children learning English or Spanish.
Regional accents also play a role in this process; children raised in an r-dropping language environment will acquire rhotic sounds at a different time, relative to all the other sounds they acquire, than children raised by people who do not drop rhotic sounds in speech, even though both accents belong to the same language.
Examples of Common English Language Phonological Processes
Stopping: Fricatives and affricates are replaced by stops. ship = tip; giraffe = diraffe
Palatal fronting: /ʃ/ or /ʒ/ are replaced by /s/ or /z/ respectively. ship = sip
Velar fronting: A back sound is replaced by a front sound. car = tar
Pre-vocalic voicing: A voiceless sound preceding a vowel is replaced by a voiced sound. car = gar
Word final devoicing: A final voiced consonant is replaced by a voiceless consonant. red = ret
Final consonant deletion: A final consonant is omitted from a word, or cut off the end of a stressed syllable. boat = bo
Consonant harmony: A consonant in a word is replaced by another consonant in the same word. cup = pup; yellow = lellow
Weak syllable deletion: Unstressed syllables are deleted from polysyllabic words. telephone = teffone
Cluster reduction: A consonant cluster is deleted or replaced. try = ty
Gliding of liquids: Liquids are replaced by glides. look = wook; red = wed
Metathesis: Sounds have their positions transposed. spaghetti = pasketti
Phonological processes can also combine within the same word or phrase. For example, combining final consonant deletion with weak syllable deletion: water bottle = wa bol.
Phonological processes in Welsh have some overlap with those in English, but there are also several processes which are less present in English, due to innate differences between Welsh and English phonology. English has a larger bank of sounds overall, but Welsh uses a consonant mutation system not present in English. Native Welsh-speaking children will have phonological processes which occur, disappear, and reoccur over time as they gain mastery of the mutation of consonants. Fricatives are usually the last phonemes a Welsh child successfully learns to distinguish and produce, and it is typical for a child to revert to earlier phonological processes on fricatives they have already acquired, when they learn to pronounce or identify a new fricative, such as the difference between /h/ and /x/, and the Welsh Ll versus /ʃ/ and /θ/. As with other languages, these reversions occur in a predictable order, and to some extent the age of a Welsh-speaking child can be approximated within just a couple months, based entirely on which sounds they pronounce successfully, and which sounds they replace or omit.
Examples of Common Welsh Language Phonological Processes
Velar fronting: "sing" canu = tanu; "light" golau = dolau
Consonant harmony: "depart" gadael = dadael (may also be interpreted as velar fronting)
Velar fronting + consonant harmony + cluster reduction: "close door" cau drws = dau dws
Metathesis + prevocalic voicing: "pick up" codi = dogi
Consonant harmony + frication of liquids (liquids are replaced by fricatives): "chair" cadair = dadaif
Cluster reduction + frication of liquids + vowel raising (mid and low vowels are replaced by high vowels): "tractor" tractor = tactyf
Iron Noder 2015, 22/30