The influence of lexical selection disruptions on articulation

Variable pronunciations reveal dynamic intra-speaker variation in speech planning

In two speech production experiments, we investigated the link between phonetic variation and the scope of advance planning at the word form encoding stage. We examined cases where a word has, in addition to the pronunciation of the word in isolation, a context-specific pronunciation variant that appears only when the following word includes specific sounds. To the extent that the speaker uses the variant specific to the following context, we can infer that the phonological content of the upcoming word is included in the current planning scope. We hypothesize that the time alignment between selection of the phonetic variant in the currently-being-encoded word and retrieval of segmental details of the upcoming word is variable from moment to moment depending on current task demands and the dynamics of lexical access for each word involved. The results showed that the use of a context-sensitive phonetic variant of /t/ (“flapping”) by English speakers reliably increased under conditions which favor advance planning. Our hypothesis was supported by evidence compatible with its three key predictions: an increase in flapping in phrases with a higher frequency following word, more flapping in a procedure with a response delay relative to a speeded response, and an attenuation of the following word frequency effect with delayed responses. This reveals that within speakers, the degree of advance planning varies continuously from moment to moment, reflecting (in part) the accessibility of form properties of individual words in the utterance.

From pre-activation to pre-updating: A threshold mechanism for commitment to strong predictions

Ample evidence suggests that during sentence processing comprehenders can "pre-activate" lexical/semantic knowledge stored in long-term memory. A relatively recent development suggests that in some cases a stronger form of prediction is employed, involving "pre-updating" the predicted content into the sentence's representation being built in working memory. The current study argues for an activation threshold mechanism by which pre-updating is initiated, within the routine processing stages of a word in a context. By combining a speeded cloze task with event-related potentials, we were able to analyze electrophysiological data measured prior to when participants were prompted to produce a completion, based on the participant's cloze response, reflecting their strongest prediction at that specific moment in time. A P600 effect reflecting pre-updating was observed in high (relative to low) constraint sentences, even in trials where the participant predicted a low cloze word. The results support a mechanism in which multiple predictions accumulate activations, "racing" toward a retrieval threshold. Once the activation level of a certain word passes the threshold, the word is integrated into the sentence representation in working memory. Pre-updating occurs if a certain prediction passes the retrieval threshold prior to its realization in the input.

The Effects of Word Frequency and Word Probability on Speech Rhythm in Dysarthria

Purpose In healthy speakers, the more frequent and probable a word is in its context, the shorter the word tends to be. This study investigated whether these probabilistic effects were similarly sized for speakers with dysarthria of different severities. Method Fifty-six speakers of New Zealand English (42 speakers with dysarthria and 14 healthy speakers) were recorded reading the Grandfather Passage. Measurements of word duration, frequency, and transitional word probability were taken. Results As hypothesized, words with a higher frequency and probability tended to be shorter in duration. There was also a significant interaction between word frequency and speech severity. This indicated that the more severe the dysarthria, the smaller the effects of word frequency on speakers' word durations. Transitional word probability also interacted with speech severity, but did not account for significant unique variance in the full model. Conclusions These results suggest that, as the severity of dysarthria increases, the duration of words is less affected by probabilistic variables. These findings may be due to reductions in the control and execution of muscle movement exhibited by speakers with dysarthria.

Using automated acoustic analysis to explore the link between planning and articulation in second language speech production

Speakers learning a second language show systematic differences from native speakers in the retrieval, planning, and articulation of speech. A key challenge in examining the interrelationship between these differences at various stages of production is the need for manual annotation of fine-grained properties of speech. We introduce a new method for automatically analyzing voice onset time (VOT), a key phonetic feature indexing differences in sound systems cross-linguistically. In contrast to previous approaches, our method allows reliable measurement of prevoicing, a dimension of VOT variation used by many languages. Analysis of VOTs, word durations, and reaction times from German-speaking learners of Spanish (Baus et al., 2013) suggest that while there are links between the factors impacting planning and articulation, these two processes also exhibit some degree of independence. We discuss the implications of these findings for theories of speech production and future research in bilingual language processing.