Publications

Abstract

The present study examined how the updating, inhibiting, and shifting abilities underlying executive control influence spoken noun-phrase production. Previous studies provided evidence that updating and inhibiting, but not shifting, influence picture naming response time (RT). However, little is known about the role of executive control in more complex forms of language production like generating phrases. We assessed noun-phrase production using picture description and a picture-word interference procedure. We measured picture description RT to assess length, distractor, and switch effects, which were assumed to reflect, respectively, the updating, inhibiting, and shifting abilities of adult participants. Moreover, for each participant we obtained scores on executive control tasks that measured verbal and nonverbal updating, nonverbal inhibiting, and nonverbal shifting. We found that both verbal and nonverbal updating scores correlated with the overall mean picture description RTs. Furthermore, the length effect in the RTs correlated with verbal but not nonverbal updating scores, while the distractor effect correlated with inhibiting scores. We did not find a correlation between the switch effect in the mean RTs and the shifting scores. However, the shifting scores correlated with the switch effect in the normal part of the underlying RT distribution. These results suggest that updating, inhibiting, and shifting each influence the speed of phrase production, thereby demonstrating a contribution of all three executive control abilities to language production.

Abstract

In this dissertation the perceptual relevance of prevoicing in Dutch was investigated. Prevoicing is the presence of vocal fold vibration during the closure of initial voiced plosives (negative voice onset time). The presence or absence of prevoicing is generally used to describe the difference between voiced and voiceless Dutch plosives. The first experiment described in this dissertation showed that prevoicing is frequently absent in Dutch and that several factors affect the production of prevoicing. A detailed acoustic analysis of the voicing distinction identified several acoustic correlates of voicing. Prevoicing appeared to be by far the best predictor. Perceptual classification data revealed that prevoicing was indeed the strongest cue that listeners use when classifying plosives as voiced or voiceless. In the cases where prevoicing was absent, other acoustic cues influenced classification, such that some of these tokens were still perceived as being voiced. In the second part of this dissertation the influence of prevoicing variation on spoken-word recognition was examined. In several cross-modal priming experiments two types of prevoicing variation were contrasted: a difference between the presence and absence of prevoicing (6 versus 0 periods of prevoicing) and a difference in the amount of prevoicing (12 versus 6 periods). All these experiments indicated that primes with 12 and 6 periods of prevoicing had the same effect on lexical decisions to the visual targets. The primes without prevoicing had a different effect, but only when their voiceless counterparts were real words. Phonetic detail appears to influence lexical access only when it is useful: In Dutch, the presence versus absence of prevoicing is informative, while the amount of prevoicing is not.

Abstract

The aim of this thesis was to gain more insight into spoken-word comprehension and the influence of sentence-contextual information on these processes using ERPs. By manipulating critical words in semantically constraining sententes, in semantic or syntactic sense, and examining the consequences in the electrophysiological signal (e.g., elicitation of ERP components such as the N400, N200, LAN, and P600), three questions were tackled: I At which moment is context information used in the spoken-word recognition process? II What is the temporal relationship between lexical selection and integration of the meaning of a spoken word into a higher-order level representeation of the preceding sentence? III What is the time course of the processing of different sources of linguistic information obtained from the context, such as phonological, semantic and syntactic information, during spoken-word comprehension? From the results of this thesis it can be concluded that sentential context already exerts an influence on spoken-word processing at approximately 200 ms after word onset. In addition, semantic integration is attempted before a spoken word can be selected on the basis of the acoustic signal, i.e. before lexical selection is completed. Finally, knowledge of the syntactic category of a word is not needed before semantic integration can take place. These findings, therefore, were interpreted as providing evidence for an account of cascaded spoken-word processing that proclaims an optimal use of contextual information during spoken-word identification. Optimal use is accomplished by allowing for semantic and syntactic processing to take place in parallel after bottom-up activation of a set of candidates, and lexical integration to proceed with a limited number of candidates that still match the acoustic input