Knowledge of a first language usually means that a learner's speech organs (tongue, alveolar ridge, hard & soft palate) have physically rehearsed certain sets of relationships many times to produce the sounds of that language. Interaction with other speakers of a first language, in most cases ones parents from an early age, gives a native English person a considerable amount of listening comprehension practice in recognising subtle differences such as 'right v light' (initial consonant sounds) or 'watch v wash' (final consonant sounds).
A second language is likely to share some of the sounds of a first, but not all. So a Japanese or a Swedish learner of English will probably not have had so many opportunities as a native speaker to produce and recognise these fine distinctions.
Titles of published practice materials (such as Tree or Three, Ship or Sheep etc.) remind us that just ONE misplaced or misunderstood sound can completely change the meaning of a word.
See the Practice Materials on this site: Mimimal Pairs - lists where each pair of word differs in just ONE consonant or vowel sound, but read on to focus on elements of pronunciation which cause much greater difficulty.
Some people use the phrase 'language interference' to describe the habit of learners to use 'the nearest sounds in their first language' in attempting to produce sounds in a second language which are new to them &/or cause them difficulty. Each language a person can use proficiently adds to their skills in producing sounds. Managing ones speech organs is a motor skill like keeping ones arm or leg muscles in good trim. Knowledge of a first language is therefore a positive gain. While we should not take the concept of 'L1 interference' completely literally, contained in the phrase is a useful reminder to L2 learners who cannot get away from their L1.
When there are three or more consonants together, native speakers do not always produce as many consonant sounds.
For example, the final consonant cluster in the word "fifths" is usually reduced to the last two consonant phonemes.
These lists practise final consonant clusters, since lists of initial consonant clusters can easily be found in a dictionary, and consonant strings at the beginnings of words generally cause fewer difficulties.
Full word lists -------for consonant clusters in final position beginning with:
|/ m /||/ p /||/ b /||/ f /||/ v /||/ θ /||/ ð /||/ n /||/ t /||/ d /||/ s /||/ z /|
|/ l /||/ r /||/ ʧ /||/ ʤ /||/ ʃ /||/ ʒ /||/ j /||/ ŋ /||/ k /||/ g /|
As well as practising consonant blends, good pronunciation materials need to include practice of elision (missing phonemes out) and assimilation: - a change in the quality of the phoneme - perhaps to a different phoneme altogether! - example: / t / changes to / p / before / m / (basket maker) / b / (cat burglar) or / p / (circuit board).
The change, in each of the above cases, results from a particular phonetic environment.
[See Wikipedia entry explaining assimilation &/or use the assimilation practice lists on this site.