Dissimilation

In phonology, particularly within historical linguistics, dissimilation is a phenomenon whereby similar consonants or vowels in a word become less similar. For example, when a /r/ sound occurs before another in the middle of a word in rhotic dialects of English, the first tends to drop out, as in "beserk" for berserk, "supprise" for surprise, "paticular" for particular, and "govenor" for governor – this does not affect the pronunciation of government, which has only one /r/, but English government tends to be pronounced "goverment", dropping out the first n.

An example where a relatively old case of phonetic dissimilation has been artificially undone in the spelling is English , whose standard pronunciation is /kərnəl/ in English. It was formerly spelt coronel and is a borrowing from French coronnel, which arose as a result of dissimilation from Italian colonnello.

There are several hypotheses as to what causes dissimilation. John Ohala posits that listeners are confused by sounds that have long-distance acoustic effects. In the case of English /r/, rhoticization spreads across much of the word (that is, in rapid speech many of the vowels may sound like they have an R in them), and it may be difficult to tell whether a word has one source of rhoticity or two. When there are two, a listener might wrongly interpret one as an acoustic effect of the other, and so mentally filter it out.

This factoring out of coarticulatory effects has been experimentally replicated. For example, Greek pakhu- (παχυ-) "thick" derives from an earlier *phakhu-. When test subjects are asked to say the *phakhu- form in casual speech, the aspiration from both consonants pervades both syllables, making the vowels breathy. Listeners hear a single effect—breathy voiced vowels—and attribute it to one rather than both of the consonants, assuming the breathiness on the other syllable to be a long-distance coarticulatory effect, thus replicating the historical change in the Greek word.

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