Representation of serial order in speech: evidence from the repeated phoneme effect in speech errors.

Previous research has shown that slips of the tongue involving the exchange of phonemes (e.g., left hemisphere----left hemisphere) are often characterized by a repeated phoneme next to the exchanging ones (the vowel /epsilon/ in the above example is next to both of the exchanging sounds, /l/ and /h/). Two experiments, which elicited slips of the tongue under controlled conditions, revealed that repeated sounds in a speech plan are contributory causes of phoneme exchanges, anticipations, and perseverations. In addition, it was found that repeated sounds induce the misordering of sounds that are not adjacent to the repeated ones, as well as those that are adjacent to the repeated ones. An analysis of a collection of natural slips also supported the conclusion that repeated sounds cause nonadjacent sounds to slip. The results are seen as inconsistent with serial order theories that propose a linear structure of sounds held together by contextual influences between adjacent phonemes.