Analysis of abstract and concrete word processing in persons with aphasia and age-matched neurologically healthy adults using fMRI.

The concreteness effect occurs in both normal and language-disordered populations. Research suggests that abstract and concrete concepts elicit differing neural activation patterns in healthy young adults, but this is undocumented in persons with aphasia (PWA). Three PWA and three age-matched controls were scanned using fMRI while processing abstract and concrete words. Consistent with current theories of abstract and concrete word processing, abstract words elicited activation in verbal areas, whereas concrete words additionally activated multimodal association areas. PWA show greater differences in neural activation than age-matched controls between abstract and concrete words, possibly due to an exaggerated concreteness effect.

How justice can affect jury: training abstract words promotes generalisation to concrete words in patients with aphasia.

Developing language treatments that not only improve trained items but also promote generalisation to untrained items is a major focus in aphasia research. This study is a replication and extension of previous work which found that training abstract words in a particular context-category promotes generalisation to concrete words but not vice versa (Kiran, Sandberg, & Abbott, 2009 ). Twelve persons with aphasia (five female) with varying types and degrees of severity participated in a generative naming treatment based on the Complexity Account of Treatment Efficacy (CATE; Thompson, Shapiro, Kiran, & Sobecks, 2003 ). All participants were trained to generate abstract words in a particular context-category by analysing the semantic features of the target words. Two other context-categories were used as controls. Ten of the twelve participants improved on the trained abstract words in the trained context-category. Eight of the ten participants who responded to treatment also generalised to concrete words in the same context-category. These results suggest that this treatment is both efficacious and efficient. We discuss possible mechanisms of training and generalisation effects.

Generalization in Aphasia Treatment: A Tutorial for Speech-Language Pathologists.

PURPOSE: Generalization has been defined and instantiated in a variety of ways over the last half-century, and this lack of consistency has created challenges for speech-language pathologists to plan for, implement, and measure generalization in aphasia treatment protocols. This tutorial provides an overview of generalization with a focus on how it relates to aphasia intervention, including a synthesis of existing principles of generalization and examples of how these can be embedded in approaches to aphasia treatment in clinical and research settings. METHOD: Three articles collectively listing 20 principles of generalization formed the foundation for this tutorial. The seminal work of Stokes and Baer (1977) focused attention on generalization in behavioral change following treatment. Two aphasia-specific resources identified principles of generalization in relation to aphasia treatment (Coppens & Patterson, 2018; Thompson, 1989). A selective literature review was conducted to identify evidence-based examples of each of these 20 principles from the extant literature. RESULTS: Five principles of generalization were synthesized from the original list of 20. Each principle was supported by studies drawn from the aphasia treatment literature to exemplify its application. CONCLUSIONS: Generalization is an essential aspect of meaningful aphasia intervention. Successful generalization requires the same dedication to strategic planning and outcome measurement as the direct training aspect of intervention. Although not all people with aphasia are likely to benefit equally from each of the principles reviewed herein, our synthesis provides information to consider for maximizing generalization of aphasia treatment outcomes. SUPPLEMENTAL MATERIAL: https://doi.org/10.23641/asha.24714399.

Novel participant-level meta-analytic evidence for AbSANT efficacy.

The current study employed interrupted time series (ITS) models to analyze all available (published and unpublished) Abstract Semantic Associative Network Training (AbSANT) data. AbSANT is a semantically focused anomia treatment that targets not only concrete but abstract words, unique among existing anomia treatments. However, evidence to date for the positive effects of AbSANT comes only from small-sample, single-subject design studies, limiting the strength of this evidence and the inferences that can be drawn from it. The statistical power and greater representativeness afforded by this larger aggregated sample enabled us to look for group-level efficacy evidence for AbSANT, examine specific questions about AbSANT's direct training and generalization effects, and identify potential predictors and mechanisms of AbSANT treatment response. We found that across 33 participants from four different data sources, AbSANT appears to be a robust word retrieval therapy protocol, with overall direct training and generalization effects that were more meaningful than exposure effects. Similar to previous smaller-sample study conclusions, we found that in this large sample, training abstract words results not only in larger direct training effects than training concrete words, but also larger generalization effects, suggesting that while AbSANT successfully improves both abstract and concrete word retrieval, it may be better suited for training abstract words. In general, direct training effects were more persistent after treatment ended than generalization effects and effects for concrete words were more persistent than for abstract words. Additionally, the effects of generalization appear to be distinct from the effects of simple exposure to words, and generalization effects are consistent with AbSANT's hypothesized mechanism of action: spreading activation from directly trained concepts to related concepts. Also consistent with this mechanism, we found that milder aphasia and both conceptual and lexical semantic processing ability predicted both direct training and generalization gains, and that executive function was predictive of generalization effects. These factors are thus important to consider when evaluating the appropriateness of AbSANT for individual clients.

Comprehension of Vernacular Features in Aphasia.

PURPOSE: Insights from linguistic variation research illustrate a linguistically diverse population, in which even speakers who can be classified as speaking a "mainstream" variety have grammatical knowledge of vernacular or "nonmainstream" features. However, there is a gap in our knowledge regarding how vernacular features are comprehended in people with aphasia (PWA). This article presents the results of a pilot study exploring how PWA respond to linguistic stimuli that include the vernacular feature, negative concord (NC), often referred to by the more colloquial term double negative (e.g., I didn't do nothing, equivalent to I didn't do anything). METHOD: Twelve PWA in the chronic stage of recovery each rated the naturalness and felicity of 48 critical sentences and 64 fillers, all of which contained two clauses, the second clause describing a consequence of the first. Ratings were analyzed using ordinal regression. RESULTS: PWA rated NC sentences as unacceptable, but felicitous-a pattern similar to that shown by neurologically intact adults in a previous study. CONCLUSIONS: These results suggest that PWA are sensitive to both social and linguistic information at levels similar to neurologically intact speakers. These results have implications for the integration of vernacular features into future research, assessment, and treatment protocols for PWA. SUPPLEMENTAL MATERIAL: https://doi.org/10.23641/asha.19027322.

Event related potential exploration of the organizational structure of abstract versus concrete words in neurologically intact younger adults.

The purpose of this study was to test the effects of concreteness and relationship type (similarity vs. association) on semantic processing using event-related potentials (ERP). Neurophysiological evidence has been found for the concreteness effect and for an effect of relationship type. This study replicated and extended these findings by investigating the interaction of concreteness and relationship type. Twenty-four neurologically healthy young adults performed lexical decision and semantic relatedness tasks while continuous scalp EEG was recorded. Larger N400 effects were found for concrete words in associative relationships than for concrete words in similarity relationships and abstract words in either type of relationship. The results are discussed in relation to the different representational frameworks account for abstract and concrete word processing.

Bilingual Abstract Semantic Associative Network Training (BAbSANT): A Polish-English case study.

INTRODUCTION: This article presents a novel approach to anomia therapy (i.e., BAbSANT: Bilingual Abstract Semantic Associative Network Training) for bilingual persons with aphasia (B-PWA) that capitalizes both on lexico-semantic theories in bilingualism and general theories of semantic organization and learning. Based on previous work, we hypothesized that training abstract words in either language would promote within-language generalization, while training in the nondominant language would promote both within- and cross-language generalization. METHODS: This case study used a single-subject A1BA2CA3 design. The participant was living with aphasia secondary to stroke and spoke both Polish and English, with Polish being his native and dominant language. Phase B consisted of abstract word training in Polish and phase C consisted of abstract word training in English. Prior to initiating therapy, in addition to a comprehensive language battery, we administered a cognitive control task to explore the relationship between cognitive control and treatment outcome. RESULTS: We found within-language generalization regardless of the trained language, replicating previous work in monolingual persons with aphasia, further supporting the utility of training abstract words. However, contrary to our second hypothesis, cross-language generalization only occurred when the stronger language was trained. CONCLUSIONS: The discussion of the results of this case study is framed within previous work and theories of bilingualism. The lack of cross-language generalization when the weaker language was trained is discussed, taking into account nonverbal cognitive control deficits. In addition to showing the efficacy of BAbSANT, these results highlight the importance of considering cognitive control as a factor influencing therapeutic outcomes in anomia treatment in bilingual PWA.

Cognitive and Linguistic Benefits of Aerobic Exercise: A State-of-the-Art Systematic Review of the Stroke Literature.

This systematic review aimed to determine how aerobic exercise affects cognition after stroke, with particular focus on aphasia and language improvement. Methodological quality was assessed with the PEDro+ scale with half of the 27 included studies rated as high quality. Data extraction focused on cognitive effects of aerobic exercise post-stroke, intervention characteristics, outcome measures, and participant characteristics. Whereas attention, memory, and executive functioning measures were common across the included studies, no study included a language-specific, performance-based measure. Seventeen studies reported positive cognitive effects, most frequently in the domains of attention, memory and executive functioning. Variability in outcome measures, intervention characteristics, and participant characteristics made it difficult to identify similarities among studies reporting positive cognitive effects of exercise or among those studies reporting null outcomes. Only three studies provided specific information about the number of individuals with aphasia included or excluded, who comprise approximately one-third of the stroke population. The review identified patent gaps in our understanding of how aerobic exercise may affect not only the cognitive domain of language post-stroke but also the broader cognitive functioning of individuals with post-stroke aphasia. Methodological limitations of the reviewed studies also warrant further examination of the direct impact of aerobic exercise on cognition post-stroke with careful attention to the selection and reporting of population, intervention, and outcomes.

Counseling in Aphasia: Information and Strategies for Speech-Language Pathologists.

Purpose The purpose of this tutorial is to provide an overview of mental health concerns of persons with aphasia (PWAs), strategies that speech-language pathologists (SLPs) can use to address the mental health concerns of PWAs within their scope of practice, guidance related to how SLPs can help facilitate access to appropriate mental health services, and suggestions for the future of pre- and postcertification education regarding counseling in aphasia for SLPs. Method This tutorial begins with a case study that is used as a reference point throughout the tutorial. It then introduces the gap in mental health services for PWAs that prompted this work, walks SLPs through common mental health concerns PWAs experience, and provides guidance for SLPs related to counseling techniques they can utilize within their sessions and referral to counseling professionals. We end by reiterating the need for more mental health awareness and training for SLPs and suggestions for incorporating more training related to addressing client mental health concerns and developing effective collaborations with rehabilitation and mental health counselors, as needed. Conclusions The mental health needs of PWAs are not being met. This is partly due to a lack of training in counseling for SLPs and a lack of training in communication techniques for rehabilitation and mental health counselors. With this tutorial, we hope to bring more awareness to the current need for mental health services for PWAs and to provide SLPs with some tools for addressing these needs among their clientele.

Abstract Semantic Associative Network Training: A Replication and Update of an Abstract Word Retrieval Therapy Program.

Purpose We report on a study that replicates previous treatment studies using Abstract Semantic Associative Network Training (AbSANT), which was developed to help persons with aphasia improve their ability to retrieve abstract words, as well as thematically related concrete words. We hypothesized that previous results would be replicated; that is, when abstract words are trained using this protocol, improvement would be observed for both abstract and concrete words in the same context-category, but when concrete words are trained, no improvement for abstract words would be observed. We then frame the results of this study with the results of previous studies that used AbSANT to provide better evidence for the utility of this therapeutic technique. We also discuss proposed mechanisms of AbSANT. Method Four persons with aphasia completed one phase of concrete word training and one phase of abstract word training using the AbSANT protocol. Effect sizes were calculated for each word type for each phase. Effect sizes for this study are compared with the effect sizes from previous studies. Results As predicted, training abstract words resulted in both direct training and generalization effects, whereas training concrete words resulted in only direct training effects. The reported results are consistent across studies. Furthermore, when the data are compared across studies, there is a distinct pattern of the added benefit of training abstract words using AbSANT. Conclusion Treatment for word retrieval in aphasia is most often aimed at concrete words, despite the usefulness and pervasiveness of abstract words in everyday conversation. We show the utility of AbSANT as a means of improving not only abstract word retrieval but also concrete word retrieval and hope this evidence will help foster its application in clinical practice.

Development of a Free Online Interactive Naming Therapy for Bilingual Aphasia.

Purpose The purpose of this ongoing project was to provide speech-language pathologists who serve culturally and linguistically diverse populations with a freely available online tool for naming therapy in a variety of languages. The purpose of this clinical focus article was to report on this resource in an effort to make known its existence, its instructions for use, and the evidence-based practices from which it was developed. Method The website, http://bilingualnamingtherapy.psu.edu/, was created by the research team in collaboration with a web programmer using Amazon Web Services. The treatment protocol for the website was adapted from an evidence-based naming intervention in which clients select and verify appropriate semantic features for the target words. This protocol comes from the work of Kiran and colleagues (Edmonds & Kiran, 2006; Kiran & Iakupova, 2011; Kiran & Lo, 2013; Kiran & Roberts, 2010; Kiran, Sandberg, Gray, Ascenso, & Kester, 2013; Krishnan, Tiwari, Kiran, & Chengappa, 2014), who showed positive benefits of this therapy within and across languages in bilingual persons with aphasia. The stimuli for the online therapy were developed in a variety of languages. First, words and semantic features were translated from English to 10 different languages. Next, surveys were created using Qualtrics software and posted on Amazon Mechanical Turk to verify picture labels and semantic features for each word in each language. The results of these surveys guided the stimuli used for each language on the website. An interactive website was developed to allow clinicians to select a set of words and progress through a series of steps. A step-by-step tutorial on how to use this website is also included in this article. Conclusions The interactive online naming therapy described in this article is currently available in English and Spanish, with Chinese under construction. Several more languages are in various stages of preparation for use on the website, and suggestions for additional languages are being actively sought. http://bilingualnamingtherapy.psu.edu/ promises to be a useful tool for speech-language pathologists who work with culturally and linguistically diverse clients. This website provides naming therapy materials, adapted from an evidence-based protocol, in a variety of languages, that have been developed based on feedback from speakers of each language to maximize cultural and linguistic appropriateness.

Hypoconnectivity of Resting-State Networks in Persons with Aphasia Compared with Healthy Age-Matched Adults.

Aphasia is a language disorder affecting more than one million people in the US. While language function has traditionally been the focus of neuroimaging research, other cognitive functions are affected in this population, which has implications not only for those specific processes but also for the interaction of language and other cognitive functions. Resting state fMRI (rs-fMRI) is a practical and informative way to explore and characterize general cognitive engagement and/or health in this population, but it is currently underutilized. The aim of this study was to explore the functional connectivity in resting state networks (RSNs) and in the semantic network in seven persons with aphasia (PWA) who were at least 6 months post onset compared with 11 neurologically healthy adults (NHA) in order to gain a more comprehensive understanding of general cognitive engagement in aphasia. These preliminary results show that PWA exhibit hypoconnectivity in the semantic network and all RSNs except the visual network. Compared with NHA, PWA appear to have fewer cross- and left-hemispheric connections. However, PWA exhibit some stronger connections than NHA within the semantic network, which could indicate compensatory mechanisms. Importantly, connectivity for RSNs appear to increase with decreasing aphasia severity and decrease with increasing lesion size. This knowledge has the potential to improve aphasia therapy by furthering the understanding of lesion effects on the cognitive system as a whole, which can guide treatment target selection and promotion of favorable neural reorganization for optimal recovery of function.

The relationships between the amount of spared tissue, percent signal change, and accuracy in semantic processing in aphasia.

Recovery from aphasia, loss of language following a cerebrovascular incident (stroke), is a complex process involving both left and right hemispheric regions. In our study, we analyzed the relationships between semantic processing behavioral data, lesion size and location, and percent signal change from functional magnetic resonance imaging (fMRI) data. This study included 14 persons with aphasia in the chronic stage of recovery (six or more months post stroke), along with normal controls, who performed semantic processing tasks of determining whether a written semantic feature matched a picture or whether two written words were related. Using region of interest (ROI) analysis, we found that left inferior frontal gyrus pars opercularis and pars triangularis, despite significant damage, were the only regions to correlate with behavioral accuracy. Additionally, bilateral frontal regions including superior frontal gyrus, middle frontal gyrus, and anterior cingulate appear to serve as an assistive network in the case of damage to traditional language regions that include inferior frontal gyrus, middle temporal gyrus, supramarginal gyrus, and angular gyrus. Right hemisphere posterior regions including right middle temporal gyrus, right supramarginal gyrus, and right angular gyrus are engaged in the case of extensive damage to left hemisphere language regions. Additionally, right inferior frontal gyrus pars orbitalis is presumed to serve a monitoring function. These results reinforce the importance of the left hemisphere in language processing in aphasia, and provide a framework for the relative importance of left and right language regions in the brain.

Changes in functional connectivity related to direct training and generalization effects of a word finding treatment in chronic aphasia.

The neural mechanisms that underlie generalization of treatment-induced improvements in word finding in persons with aphasia (PWA) are currently poorly understood. This study aimed to shed light on changes in functional network connectivity underlying generalization in aphasia. To this end, we used fMRI and graph theoretic analyses to examine changes in functional connectivity after a theoretically-based word-finding treatment in which abstract words were used as training items with the goal of promoting generalization to concrete words. Ten right-handed native English-speaking PWA (7 male, 3 female) ranging in age from 47 to 75 (mean=59) participated in this study. Direct training effects coincided with increased functional connectivity for regions involved in abstract word processing. Generalization effects coincided with increased functional connectivity for regions involved in concrete word processing. Importantly, similarities between training and generalization effects were noted as were differences between participants who generalized and those who did not.

Rehabilitation in bilingual aphasia: evidence for within- and between-language generalization.

PURPOSE: The goal of this study was to examine if there was a principled way to understand the nature of rehabilitation in bilingual aphasia such that patterns of acquisition and generalization are predictable and logical. METHOD: Seventeen Spanish-English bilingual individuals with aphasia participated in the experiment. For each participant, three sets of stimuli were developed for each language: (a) English Set 1, (b) English Set 2 (semantically related to each item in English Set 1), (c) English Set 3 (unrelated control items), (d) Spanish Set 1 (translations of English Set 1), (e) Spanish Set 2 (translations of English Set 2; semantically related to each item in Spanish Set 1), and (f) Spanish Set 3 (translations of English Set 3; unrelated control items). A single-subject experimental multiple baseline design across participants was implemented. Treatment was conducted in 1 language, but generalization to within- and between-language untrained items was examined. RESULTS: Treatment for naming on Set 1 items resulted in significant improvement (i.e., effect size >4.0) on the trained items in 14/17 participants. Of the 14 participants who showed improvement, within-language generalization to semantically related items was observed in 10 participants. Between-language generalization to the translations of trained items was observed in 5 participants, and between-language generalization to the translations of the untrained semantically related items was observed in 6 participants. CONCLUSION: The results of this study demonstrated within- and between-language patterns that were variable across participants. These differences are indicative of the interplay between facilitation (generalization) and inhibition.

A Computational Account of Bilingual Aphasia Rehabilitation.

Current research on bilingual aphasia highlights the paucity in recommendations for optimal rehabilitation for bilingual aphasic patients (Roberts & Kiran, 2007; Edmonds & Kiran, 2006). In this paper, we have developed a computational model to simulate an English-Spanish bilingual language system in which language representations can vary by age of acquisition (AoA) and relative proficiency in the two languages to model individual participants. This model is subsequently lesioned by varying connection strengths between the semantic and phonological networks and retrained based on individual patient demographic information to evaluate whether or not the model's prediction of rehabilitation matched the actual treatment outcome. In most cases the model comes close to the target performance subsequent to language therapy in the language trained, indicating the validity of this model in simulating rehabilitation of naming impairment in bilingual aphasia. Additionally, the amount of cross-language transfer is limited both in the patient performance and in the model's predictions and is dependent on that specific patient's AoA, language exposure and language impairment. It also suggests how well alternative treatment scenarios would have fared, including some cases where the alternative would have done better. Overall, the study suggests how computational modeling could be used in the future to design customized treatment recipes that result in better recovery than is currently possible.

Typicality mediates performance during category verification in both ad-hoc and well-defined categories.

BACKGROUND: The typicality effect is present in neurologically intact populations for natural, ad-hoc, and well-defined categories. Although sparse, there is evidence of typicality effects in persons with chronic stroke aphasia for natural and ad-hoc categories. However, it is unknown exactly what influences the typicality effect in this population. AIMS: The present study explores the possible contributors to the typicality effect in persons with aphasia by analyzing and comparing data from both normal and language-disordered populations, from persons with aphasia with more semantic impairment versus those with less semantic impairment, and from two types of categories with very different boundary structure (ad-hoc vs. well-defined). METHODS AND PROCEDURES: A total of 40 neurologically healthy adults (20 older, 20 younger) and 35 persons with aphasia (20 LSI (less-semantically impaired) patients, 15 MSI (more-semantically impaired) patients) participated in the study. Participants completed one of two tasks: either category verification for ad-hoc categories or category verification for well-defined categories. OUTCOMES AND RESULTS: Neurologically healthy participants showed typicality effects for both ad-hoc and well-defined categories. MSI patients showed a typicality effect for well-defined categories, but not for ad-hoc categories, whereas LSI patients showed a typicality effect for ad-hoc categories, but not for well-defined categories. CONCLUSIONS: These results suggest that the degree of semantic impairment mediates the typicality effect in persons with aphasia depending on the structure of the category. LEARNING OUTCOMES: After reading this article, the reader should be able to: (1) Describe the typicality effect and in which populations it occurs. (2) Explain how the typicality effect might change depending on category structure. (3) summarize how semantic impairment influences category representation and/or access.

Effects of syntactic complexity, semantic reversibility, and explicitness on discourse comprehension in persons with aphasia and in healthy controls.

PURPOSE: Prior studies of discourse comprehension have concluded that the deficits of persons with aphasia (PWA) in syntactically based comprehension of sentences in isolation are not predictive of deficits in comprehension of sentences in discourse (Brookshire & Nicholas, 1984; Caplan & Evans, 1990). However, these studies used semantically constrained sentences in discourse, which do not require syntactic analysis to be understood. A discourse task was developed to assess the effect of syntactic complexity, among other factors, on discourse comprehension in PWA. METHOD: Thirty-eight PWA and 30 neurologically healthy control participants were presented with passages that contained 2-3 semantically reversible sentences that were either syntactically simple or syntactically complex. The passages were presented auditorily, and comprehension was assessed with the auditory and written presentation of 4 multiple-choice questions immediately following each passage. RESULTS: Passages with syntactically simple sentences were better understood than passages with syntactically complex sentences. Moreover, semantically constrained sentences were more likely to be accurately interpreted than semantically reversible sentences. Comprehension accuracy on our test correlated positively with comprehension accuracy on an existing test. CONCLUSION: The presence of semantically reversible, syntactically complex sentences in a passage affects comprehension of the passage in both PWA and neurologically healthy individuals.

Development of a theoretically based treatment for sentence comprehension deficits in individuals with aphasia.

PURPOSE: Two new treatments, 1 based on sentence to picture matching (SPM) and the other on object manipulation (OM), that train participants on the thematic roles of sentences using pictures or by manipulating objects were piloted. METHOD: Using a single-subject multiple-baseline design, sentence comprehension was trained on the affected sentence type in 1 task-related protocol in 15 participants with aphasia. The 2 tasks were SPM and OM; the treatment stimuli were object relatives, object clefts, passives, and unaccusatives, as well as two control structures-object relatives with a complex noun phrase (NP) and active sentences with three NPs. RESULTS: The criteria for efficacious treatment was an increase in the level of performance from the pretreatment probes to the posttreatment probes for the treated structure such that accuracy rose from at or below chance to above chance and either (a) accuracy rose by 33% or (b) the effect size was 2.6. Based on these criteria, the success rate for training the target structure was 2/6 participants in the SPM condition and 4/7 participants in the OM condition. CONCLUSION: The outcome of this study illustrates the utility of this theoretically motivated and efficacious treatment for sentence comprehension deficits in individuals with aphasia.

Treatment of category generation and retrieval in aphasia: effect of typicality of category items.

PURPOSE: Kiran and colleagues (Kiran, 2007, 2008; Kiran & Johnson, 2008; Kiran & Thompson, 2003) previously suggested that training atypical examples within a semantic category is a more efficient treatment approach to facilitating generalization within the category than training typical examples. In the present study, the authors extended previous work examining the notion of semantic complexity within goal-derived (ad hoc) categories in individuals with aphasia. Methods Six individuals with fluent aphasia (age range = 39-84 years) and varying degrees of naming deficits and semantic impairments were involved. Thirty typical and atypical items, each from 2 categories, were selected after an extensive stimulus norming task. Generative naming for the 2 categories was tested during baseline and treatment. RESULTS: As predicted, training atypical examples in the category resulted in generalization to untrained typical examples in 5 of 5 patient-treatment conditions. In contrast, training typical examples (which was examined in 3 conditions) produced mixed results. One patient showed generalization to untrained atypical examples, whereas 2 patients did not show generalization to untrained atypical examples. CONCLUSION: Results of the present study supplement existing data on the effect of a semantically based treatment for lexical retrieval by manipulating the typicality of category examples.