Publications

Abstract

Background

The factors that contribute to language alternation by bilingual speakers with aphasia have been debated. Some studies suggest that atypical language mixing results from impairments in language control, while others posit that mixing is a way to enhance communicative effectiveness. To address this question, most prior research examined the appropriateness of language mixing in connected speech tasks.
Aims

The goal of this study was to provide new insight into the question whether language mixing in aphasia reflects a strategy to enhance verbal effectiveness or involuntary behaviour resulting from impaired language control.
Methods & procedures

Semi-structured web-based interviews with bilingual speakers with aphasia (N = 19) with varying language backgrounds were conducted. The interviews were transcribed and coded for: (1) Self-reports regarding language control and compensation, (2) instances of language mixing, and (3) in two cases, instances of repair initiation.
Outcomes & results

The results showed that several participants reported language control difficulties but that the knowledge of additional languages could also be recruited to compensate for lexical retrieval problems. Most participants showed no or very few instances of mixing and the observed mixes appeared to adhere to the pragmatic context and known functions of switching. Three participants exhibited more marked switching behaviour and reported corresponding difficulties with language control. Instances of atypical mixing did not coincide with clear problems initiating conversational repair.
Conclusions

Our study highlights the variability in language mixing patterns of bilingual speakers with aphasia. Furthermore, most of the individuals in the study appeared to be able to effectively control their languages, and to alternate between their languages for compensatory purposes. Control deficits resulting in atypical language mixing were observed in a small number of participants.

Abstract

Whereas it has long been assumed that competition plays a role in lexical selection in word production (e.g., Levelt, Roelofs, & Meyer, 1999), recently Finkbeiner and Caramazza (2006) argued against the competition assumption on the basis of their observation that visible distractors yield semantic interference in picture naming, whereas masked distractors yield semantic facilitation. We examined an alternative account of these findings that preserves the competition assumption. According to this account, the interference and facilitation effects of distractor words reflect whether or not distractors are strong enough to exceed a threshold for entering the competition process. We report two experiments in which distractor strength was manipulated by means of coactivation and visibility. Naming performance was assessed in terms of mean response time (RT) and RT distributions. In Experiment 1, with low coactivation, semantic facilitation was obtained from clearly visible distractors, whereas poorly visible distractors yielded no semantic effect. In Experiment 2, with high coactivation, semantic interference was obtained from both clearly and poorly visible distractors. These findings support the competition threshold account of the polarity of semantic effects in naming.

Abstract

Picture–word interference is a widely employed paradigm to investigate lexical access in word production: Speakers name pictures while trying to ignore superimposed distractor words. The distractor can be congruent to the picture (pictured cat, word cat), categorically related (pictured cat, word dog), or unrelated (pictured cat, word pen). Categorically related distractors slow down picture naming relative to unrelated distractors, the so-called semantic interference. Categorically related distractors slow down picture naming relative to congruent distractors, analogous to findings in the colour–word Stroop task. The locus of semantic interference and Stroop-like effects in naming performance has recently become a topic of debate. Whereas some researchers argue for a pre-lexical locus of semantic interference and a lexical locus of Stroop-like effects, others localise both effects at the lexical selection stage. We investigated the time course of semantic and Stroop-like interference effects in overt picture naming by means of event-related potentials (ERP) and time–frequency analyses. Moreover, we employed cluster-based permutation for statistical analyses. Naming latencies showed semantic and Stroop-like interference effects. The ERP waveforms for congruent stimuli started diverging statistically from categorically related stimuli around 250 ms. Deflections for the categorically related condition were more negative-going than for the congruent condition (the Stroop-like effect). The time–frequency analysis revealed a power increase in the beta band (12–30 Hz) for categorically related relative to unrelated stimuli roughly between 250 and 370 ms (the semantic effect). The common time window of these effects suggests that both semantic interference and Stroop-like effects emerged during lexical selection.

Abstract

We examined the contribution of executive control to individual differences in response time (RT) for naming objects and actions. Following Miyake, Friedman, Emerson, Witzki, Howerter, and Wager (2000), executive control was assumed to include updating, shifting, and inhibiting abilities, which were assessed using operation-span, task switching, and stop-signal tasks, respectively. Study 1 showed that updating ability was significantly correlated with the mean RT of action naming, but not of object naming. This finding was replicated in Study 2 using a larger stimulus set. Inhibiting ability was significantly correlated with the mean RT of both action and object naming, whereas shifting ability was not correlated with the mean naming RTs. Ex-Gaussian analyses of the RT distributions revealed that updating ability was correlated with the distribution tail of both action and object naming, whereas inhibiting ability was correlated with the leading edge of the distribution for action naming and the tail for object naming. Shifting ability provided no independent contribution. These results indicate that the executive control abilities of updating and inhibiting contribute to the speed of naming objects and actions, although there are differences in the way and extent these abilities are involved.