Dear Leader, I am suplised you don't know of this famous plobrem. The previous sentence was meant to read: Dear Reader, I am surprised you don't know of this famous problem. Why the insidious transpositions?
Listeners to Akan English speakers may have heard of an apparent slip of tongue which occurs when the speaker tries to pronounce words with the letters r or l in them. Contrary to popular belief, I contend that this is not a slip of tongue but in fact, a normal extension of Akan phonetics--a mere consequence of fluid bilingualism.
Akan refers to a collection of people who are mostly found in the Southern part of modern day Ghana. They form about 50% of the population. Thare are also some Akans in Cote d'Ivoire but they are a significantly smaller population. The Akans speak a collection of languages (some may argue, dialects) from the Kwa language family that are mostly mutually intelligible: Asante, Akuapem, Fante, Bono, to list a few. The speakers of Asante appear to be the ones who suffer the most from this "error," but it may not be an error due to ignorance of the correct pronunciation, but, rather, one resulting from an invalid extension of their Kwan articulatory instincts.
The framework that dictates the transcription of Twi was created by Johann Gottlieb Christaller, a German Basel missionary who started his missionary as well as philological work among the Akuapems at Akropong. His primary preoccupation was with formalising the language in order to translate the Bible into Twi. Christaller's legacy extends beyond his immense contributions to Twi transcription; his work sparked a chain of literary works, including several dictionaries, a book of Twi proverbs, and a magazine promoting the use of Ghanaian languages. It is noteworthy that even though all of these works are more than a century old, they are yet to be matched in scope and influence.
The Twi alphabet has 22 characters or letters and it inherits all of the English alphabet except the letters c, j, q, v, x and z. It then adds another two letters: ɛ and ɔ. Here, it is in order to acknowledge one difference between the dialects. In Fante, z is used in names like Dadzie or dzi (English: eat, deal, mind). The other differences result from the combination of letters to produce sounds as well as the differences in accenting patterns on syllables.
How does allophony interplay with all of these? Allophony is not peculiar to Twi. It occurs in a language when different pronunciations of a phoneme do not result in a distinction in meaning. For instance, those familiar with the differences between British and American English know that for a certain ubiquitous fluid that is essential to life, one group prefers to call it water (with an emphasis on the /t/) while the other group prefers to say wader or warer. In this case /t/, /d/ and /r/ are allophones in the English language. Similarly, in Twi, sometimes /r/ and /l/ are allophones. Bɔɔdedwo (English: roasted plantain) is sometimes pronounced bɔɔledwo or bɔɔredwo. Here, the allophony is with /r/, /l/ and /d/. The /r/ and /d/ allophony is just like the one in English. Linguists have a special name for that: consonant lenition. The /d/ stop is harder to pronounce than the rhodic /r/ which is in turn harder to pronounce than /l/. The lenition is revealed in a phrase like m'ani abede (English: I am serious, where the /d/ in abede is used for emphasis) instead of m'ani abere.
The above explanation would be perfect in English. That is, Twi speakers, especially those who know the language very well through experience, often fall into the ARLAP trap, forgetting the R-L allophony rule does not apply in English. However, historically, the letter /l/ was never used in Twi. Evidence of this is borne out by the fact that all words with /l/ are borrowed from a different language eg. lɔɔre (English: car. From lorry.) and bɔɔla (English: refuse dump. From English boiler.). So, transformation of /r/ to /l/ may have been the result of a natural tendency to ease speaking, but this is a hypothesis. It would imply that words with /r/ would be more susceptible to the ARLAP than, say, words with /l/. I don't not have the statistics on this, but that may be a litmus test for this theory.