Academic journal article Memory & Cognition

The Role of Inhibition in the Production of Disfluencies

Academic journal article Memory & Cognition

The Role of Inhibition in the Production of Disfluencies

Article excerpt

Disfluency is a common occurrence in speech and is generally thought to be related to difficulty in the production system. One unexplored issue is the extent to which inhibition is required to prevent incorrect speech plans from being articulated. Therefore, we examined disfluency production in participants with attention-deficit/hyperactivity disorder (ADHD), which is linked to deficits in inhibitory function and response suppression (Nigg, 2001). Participants completed a sentence production task in which they were presented with two pictures and a verb and their task was to produce a sentence. If inhibition plays a role in preventing incorrect speech plans, we would expect ADHD participants to produce more repetition and repair disfluencies than would non-ADHD controls. The results showed that one subtype of ADHD (i.e., the combined) produced more repair disfluencies as task demands increased. We conclude that the production system relies on inhibitory control in order to prevent errors in language production.

Spoken language often contains various types of disfluency. These range from filled pauses, such as uh and um, to corrections (Fox Tree, 1995). Corrections include repetitions and repairs. Repetitions refer to unintended repeats of a word or a string of words (e.g., The . . . the other one). Repairs occur when a speaker stops and then starts over with some new word or phrase (e.g., Turn left . . . turn right at the light). There has been a great deal of work on the effects of disfluency on language comprehension, and this work has revealed that the comprehension system can be affected by disfluencies in various ways. For example, it is well established from corpus work that disfluencies occur more frequently at the beginning of clauses and other complex constituents (Ford, 1982; Goldman-Eisler, 1968). Bailey and Ferreira (2003) therefore hypothesized that disfluencies may have an impact on the processing of garden path sentences, which involve a choice between a simple and a more complex structure. They found that when a disfluency (i.e., uh) was placed at the choice point, comprehenders were more likely to pursue the more complex alternative, as compared with a sentence that did not contain a disfluency. This suggests that the comprehension system can use the presence of a disfluency to make decisions about alternate structural analyses (see also Ferreira & Bailey, 2004).

In another line of work, Arnold, Tanenhaus, Altmann, and Fagnano (2004) investigated the effects of disfluency in a referential communication task. They showed that the presence of a disfluency led to faster identification of an object when it preceded a discourse-new referent, as compared with a referent that had already been established in the discourse. Fox Tree (2001) also found faster recognition for upcoming words in the speech stream when they were preceded by uh, as compared with the same utterances that had the disfluency excised. She concluded that disfluency signals a delay and heightens a listener's attention to the upcoming word, which facilitates recognition. Corley, MacGregor, and Donaldson (2007) showed a reduced N400 component for contextually unpredictable words following a disfluency, which suggests that the presence of a disfluency can ease semantic integration (Kutas & Hillyard, 1980).

Taken together, this body of work demonstrates that disfluencies can have a wide range of beneficial effects on language comprehension (Brennan & Schober, 2001; Lau & Ferreira, 2005). It is surprising that there has been comparably less work on the factors that affect the production of disfluency. Work focusing on production has used two main methodologies. The first is the examination of natural language corpora to identify the distribution of disfluencies in naturally occurring speech (Clark & Fox Tree, 2002). The second approach makes use of experimental tasks designed to elicit disfluencies, mainly through manipulations of time pressure and nameability of the objects that a speaker must refer to (Oomen & Postma, 2001). …

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