Esther Janse

What do verbal fluency tasks measure? Predictors of verbal fluency performance in older adults

This study examined the contributions of verbal ability and executive control to verbal fluency performance in older adults (n = 82). Verbal fluency was assessed in letter and category fluency tasks, and performance on these tasks was related to indicators of vocabulary size, lexical access speed, updating, and inhibition ability. In regression analyses the number of words produced in both fluency tasks was predicted by updating ability, and the speed of the first response was predicted by vocabulary size and, for category fluency only, lexical access speed. These results highlight the hybrid character of both fluency tasks, which may limit their usefulness for research and clinical purposes.

Comprehension of a novel accent by young and older listeners.

The authors investigated perceptual learning of a novel accent in young and older listeners through measuring speech reception thresholds (SRTs) using speech materials spoken in a novel-unfamiliar-accent. Younger and older listeners adapted to this accent, but older listeners showed poorer comprehension of the accent. Furthermore, perceptual learning differed across groups: The older listeners stopped learning after the first block, whereas younger listeners showed further improvement with longer exposure. Among the older participants, hearing acuity predicted the SRT as well as the effect of the novel accent on SRT. Finally, a measure of executive function predicted the impact of accent on SRT.

Word perception in fast speech: artificially time-compressed vs. naturally produced fast speech

Natural fast speech differs from normal-rate speech with respect to its temporal pattern. Previous results showed that word intelligibility of heavily artificially time-compressed speech could not be improved by making its temporal pattern more similar to that of natural fast speech. This might have been due to the extrapolation of timing rules for natural fast speech to rates that are much faster than can be attained by human speakers. The present study investigates whether, at a speech rate that human speakers can attain, artificially time-compressed speech is easier to process if its timing pattern is similar to that of naturally produced fast speech. Our first experiment suggests, however, that word processing speed was slowed down, relative to linear compression. In a second experiment, word processing of artificially time-compressed speech was compared with processing of naturally produced fast speech. Even when naturally produced fast speech is perfectly intelligible, its less careful articulation, combined with the changed timing pattern, slows down processing, relative to linearly time-compressed speech. Furthermore, listeners preferred artificially time-compressed speech over naturally produced fast speech. These results suggest that linearly time-compressed speech has both a temporal and a segmental advantage over natural fast speech. � 2003 Elsevier B.V. All rights reserved.

Predicting foreign-accent adaptation in older adults

We investigated comprehension of and adaptation to speech in an unfamiliar accent in older adults. Participants performed a speeded sentence verification task for accented sentences: one group upon auditory-only presentation, and the other group upon audiovisual presentation. Our questions were whether audiovisual presentation would facilitate adaptation to the novel accent, and which cognitive and linguistic measures would predict adaptation. Participants were therefore tested on a range of background tests: hearing acuity, auditory verbal short-term memory, working memory, attention-switching control, selective attention, and vocabulary knowledge. Both auditory-only and audiovisual groups showed improved accuracy and decreasing response times over the course of the experiment, effectively showing accent adaptation. Even though the total amount of improvement was similar for the auditory-only and audiovisual groups, initial rate of adaptation was faster in the audiovisual group. Hearing sensitivity and short-term and working memory measures were associated with efficient processing of the novel accent. Analysis of the relationship between accent comprehension and the background tests revealed furthermore that selective attention and vocabulary size predicted the amount of adaptation over the course of the experiment. These results suggest that vocabulary knowledge and attentional abilities facilitate the attention-shifting strategies proposed to be required for perceptual learning.

Perceptual learning of time-compressed and natural fast speech

Speakers vary their speech rate considerably during a conversation, and listeners are able to quickly adapt to these variations in speech rate. Adaptation to fast speech rates is usually measured using artificially time-compressed speech. This study examined adaptation to two types of fast speech: artificially time-compressed speech and natural fast speech. Listeners performed a speeded sentence verification task on three series of sentences: normal-speed sentences, time-compressed sentences, and natural fast sentences. Listeners were divided into two groups to evaluate the possibility of transfer of learning between the time-compressed and natural fast conditions. The first group verified the natural fast before the time-compressed sentences, while the second verified the time-compressed before the natural fast sentences. The results showed transfer of learning when the time-compressed sentences preceded the natural fast sentences, but not when natural fast sentences preceded the time-compressed sentences. The results are discussed in the framework of theories on perceptual learning. Second, listeners show adaptation to the natural fast sentences, but performance for this type of fast speech does not improve to the level of time-compressed sentences.

Word-level intelligibility of time-compressed speech: prosodic and segmental factors

In this study we investigate whether speakers, in line with the predictions of the Hyper- and Hypospeech theory, speed up most during the least informative parts and less during the more informative parts, when they are asked to speak faster. We expected listeners to benefit from these changes in timing, and our main goal was to find out whether making the temporal organisation of artificially time-compressed speech more like that of natural fast speech would improve intelligibility over linear time compression. Our production study showed that speakers reduce unstressed syllables more than stressed syllables, thereby making the prosodic pattern more pronounced. We extrapolated fast speech timing to even faster rates because we expected that the more salient prosodic pattern could be exploited in difficult listening situations. However, at very fast speech rates, applying fast speech timing worsens intelligibility. We argue that the non-uniform way of speeding up may not be due to an underlying communicative principle, but may result from speakers inability to speed up otherwise. As both prosodic and segmental information contribute to word recognition, we conclude that extrapolating fast speech timing to extremely fast rates distorts this balance between prosodic and segmental information. 2002 Elsevier B.V. All rights reserved.

Individual differences in working memory and processing speed predict anticipatory spoken language processing in the visual world

ABSTRACT Several mechanisms of predictive language processing have been proposed. The possible influence of mediating factors such as working memory and processing speed, however, has largely been ignored. We sought to find evidence for such an influence using an individual differences approach. 105 participants from 32–77 years of age received spoken instructions (e.g. “Kijk naar deCOM afgebeelde pianoCOM”– look at the displayed piano) while viewing 4 objects. Articles (Dutch “het” or “de”) were gender-marked such that the article agreed in gender only with the target. Participants could thus use article gender information to predict the target. Multiple regression analyses showed that enhanced working memory abilities and faster processing speed predicted anticipatory eye movements. Models of predictive language processing therefore must take mediating factors into account. More generally, our results are consistent with the notion that working memory grounds language in space and time, linking linguistic and visual–spatial representations.

Coping with gradient forms of /t/-deletion and lexical ambiguity in spoken word recognition

This study investigates how listeners cope with gradient forms of deletion of word-final /t/ when recognising words in a phonological context that makes /t/-deletion viable. A corpus study confirmed a high incidence of /t/-deletion in an /st#b/ context in Dutch. A discrimination study showed that differences between released /t/, unreleased /t/ and fully deleted /t/ in this specific /st#b/ context were salient. Two on-line experiments were carried out to investigate whether lexical activation might be affected by this form variation. Even though unreleased and released variants were processed equally fast by listeners, a detailed analysis of the unreleased condition provided evidence for gradient activation. Activating a target ending in /t/ is slowest for the most reduced variant because phonological context has to be taken into account. Importantly, activation for a target with /t/ in the absence of cues for /t/ is reduced if there is a surface-matching lexical competitor.

Lexical Competition Effects in Aphasia: Deactivation of Lexical Candidates in Spoken Word Processing.

Research has shown that Brocas and Wernickes aphasic patients show different impairments in auditory lexical processing. The results of an experiment with form-overlapping primes showed an inhibitory effect of form-overlap for control adults and a weak inhibition trend for Brocas aphasic patients, but a facilitatory effect of form-overlap was found for Wernickes aphasic participants. This suggests that Wernickes aphasic patients are mainly impaired in suppression of once-activated word candidates and selection of one winning candidate, which may be related to their problems in auditory language comprehension.

A non-auditory measure of interference predicts distraction by competing speech in older adults

ABSTRACT In this study, older adults monitored for pre-assigned target sounds in a target talkers speech in a quiet (no noise) condition and in a condition with competing-talker noise. The question was to which extent the impact of the competing-talker noise on performance could be predicted from individual hearing loss and from a cognitive measure of inhibitory abilities, i.e., a measure of Stroop interference. The results showed that the non-auditory measure of Stroop interference predicted the impact of distraction on performance, over and above the effect of hearing loss. This suggests that individual differences in inhibitory abilities among older adults relate to susceptibility to distracting speech.