Serial order in phonological encoding: an exploration of the 'word onset effect' using laboratory-induced errors.

One controversial phenomenon concerning slips of the tongue is the tendency for the onsets of words to slip more frequently than segments at other word positions. Some researchers attribute this effect to the phonological properties of word onsets, while others suggest it reflects something specific about the role played by the word onset during phonological recovery and/or sequencing. The study reported here examined these two possibilities using a tongue-twister paradigm in which subjects were asked to repeatedly recite a visually-presented word quadruple. The lexical status of the words in target sequences was manipulated independently of their broader phonological characteristics (overall sonority profile and consonant composition) by simply altering their constituent vowels (e.g. case port bed moon vs. koss pait bod marn). Errors elicited on real word targets were found to exhibit a strong word onset effect; this effect was entirely confined to between-word contextual errors. However, nonword targets generated no word onset effect, either overall or on between-word errors considered alone. These findings suggest that the word onset effect cannot be entirely attributed to phonological factors, but instead reflects something about the larger role word onsets play in (real word) speech planning. A new account is offered, which attributes the word onset effect to order-based competition between items at the lexical level.