Response Latencies During Confrontation Picture Naming in Aphasia: Are Proxy Measurements Sufficient?

PURPOSE: Anomia, or word-finding difficulty, is a prevalent and persistent feature of aphasia, a neurogenic language disorder affecting millions of people in the United States. Anomia assessments are essential for measuring performance and monitoring outcomes in clinical settings. This study aims to evaluate the reliability of response time (RT) annotation based on spectrograms and assess the predictive utility of proxy RTs collected during computerized naming tests. METHOD: Archival data from 10 people with aphasia were used. Trained research assistants phonemically transcribed participants' responses, and RTs were generated from the onset of picture stimulus to the initial phoneme of the first complete attempt. RTs were measured in two ways: hand-generated RTs (from spectrograms) and proxy RTs (automatically extracted online). Interrater agreement was evaluated based on interclass correlation coefficients and generalizability theory tools including variance partitioning and the φ-coefficient. The predictive utility of proxy RTs was evaluated within a linear mixed-effects framework. RESULTS: RT annotation reliability showed near-perfect agreement across research assistants (φ-coefficient = .93), and the variance accounted for by raters was negligible. Furthermore, proxy RTs significantly and strongly predicted hand-annotated RTs (R2 = ~0.82), suggesting their utility as an alternative measure. CONCLUSIONS: The study confirms the reliability of RT annotation and demonstrates the predictive utility of proxy RTs in estimating RTs during computerized naming tests. Incorporating proxy RTs can enhance clinical assessments, providing additional information for cognitive measurement. Further research with larger samples and exploring the impact of using proxy RTs in different psychometric models could optimize clinical protocols and improve communication interventions for individuals with aphasia.

Automating Intended Target Identification for Paraphasias in Discourse Using a Large Language Model.

PURPOSE: To date, there are no automated tools for the identification and fine-grained classification of paraphasias within discourse, the production of which is the hallmark characteristic of most people with aphasia (PWA). In this work, we fine-tune a large language model (LLM) to automatically predict paraphasia targets in Cinderella story retellings. METHOD: Data consisted of 332 Cinderella story retellings containing 2,489 paraphasias from PWA, for which research assistants identified their intended targets. We supplemented these training data with 256 sessions from control participants, to which we added 2,415 synthetic paraphasias. We conducted four experiments using different training data configurations to fine-tune the LLM to automatically "fill in the blank" of the paraphasia with a predicted target, given the context of the rest of the story retelling. We tested the experiments' predictions against our human-identified targets and stratified our results by ambiguity of the targets and clinical factors. RESULTS: The model trained on controls and PWA achieved 50.7% accuracy at exactly matching the human-identified target. Fine-tuning on PWA data, with or without controls, led to comparable performance. The model performed better on targets with less human ambiguity and on paraphasias from participants with fluent or less severe aphasia. CONCLUSIONS: We were able to automatically identify the intended target of paraphasias in discourse using just the surrounding language about half of the time. These findings take us a step closer to automatic aphasic discourse analysis. In future work, we will incorporate phonological information from the paraphasia to further improve predictive utility. SUPPLEMENTAL MATERIAL: https://doi.org/10.23641/asha.24463543.

Accuracy of Naming Error Profiles Elicited From Adaptive Short Forms of the Philadelphia Naming Test.

PURPOSE: The purpose of this study was to evaluate whether a short-form computerized adaptive testing (CAT) version of the Philadelphia Naming Test (PNT) provides error profiles and model-based estimates of semantic and phonological processing that agree with the full test. METHOD: Twenty-four persons with aphasia took the PNT-CAT and the full version of the PNT (hereinafter referred to as the "full PNT") at least 2 weeks apart. The PNT-CAT proceeded in two stages: (a) the PNT-CAT30, in which 30 items were selected to match the evolving ability estimate with the goal of producing a 50% error rate, and (b) the PNT-CAT60, in which an additional 30 items were selected to produce a 75% error rate. Agreement was evaluated in terms of the root-mean-square deviation of the response-type proportions and, for individual response types, in terms of agreement coefficients and bias. We also evaluated agreement and bias for estimates of semantic and phonological processing derived from the semantic-phonological interactive two-step model (SP model) of word production. RESULTS: The results suggested that agreement was poorest for semantic, formal, mixed, and unrelated errors, all of which were underestimated by the short forms. Better agreement was observed for correct and nonword responses. SP model weights estimated by the short forms demonstrated no substantial bias but generally inadequate agreement with the full PNT, which itself showed acceptable test-retest reliability for SP model weights and all response types except for formal errors. DISCUSSION: Results suggest that the PNT-CAT30 and the PNT-CAT60 are generally inadequate for generating naming error profiles or model-derived estimates of semantic and phonological processing ability. Post hoc analyses suggested that increasing the number of stimuli available in the CAT item bank may improve the utility of adaptive short forms for generating error profiles, but the underlying theory also suggests that there are limitations to this approach based on a unidimensional measurement model. SUPPLEMENTAL MATERIAL: https://doi.org/10.23641/asha.22320814.

Item Response Theory Modeling of the Verb Naming Test.

PURPOSE: Item response theory (IRT) is a modern psychometric framework with several advantageous properties as compared with classical test theory. IRT has been successfully used to model performance on anomia tests in individuals with aphasia; however, all efforts to date have focused on noun production accuracy. The purpose of this study is to evaluate whether the Verb Naming Test (VNT), a prominent test of action naming, can be successfully modeled under IRT and evaluate its reliability. METHOD: We used responses on the VNT from 107 individuals with chronic aphasia from AphasiaBank. Unidimensionality and local independence, two assumptions prerequisite to IRT modeling, were evaluated using factor analysis and Yen's Q 3 statistic (Yen, 1984), respectively. The assumption of equal discrimination among test items was evaluated statistically via nested model comparisons and practically by using correlations of resulting IRT-derived scores. Finally, internal consistency, marginal and empirical reliability, and conditional reliability were evaluated. RESULTS: The VNT was found to be sufficiently unidimensional with the majority of item pairs demonstrating adequate local independence. An IRT model in which item discriminations are constrained to be equal demonstrated fit equivalent to a model in which unique discrimination parameters were estimated for each item. All forms of reliability were strong across the majority of IRT ability estimates. CONCLUSIONS: Modeling the VNT using IRT is feasible, yielding ability estimates that are both informative and reliable. Future efforts are needed to quantify the validity of the VNT under IRT and determine the extent to which it measures the same construct as other anomia tests. SUPPLEMENTAL MATERIAL: https://doi.org/10.23641/asha.22329235.

ParAlg: A Paraphasia Algorithm for Multinomial Classification of Picture Naming Errors.

PURPOSE: A preliminary version of a paraphasia classification algorithm (henceforth called ParAlg) has previously been shown to be a viable method for coding picture naming errors. The purpose of this study is to present an updated version of ParAlg, which uses multinomial classification, and comprehensively evaluate its performance when using two different forms of transcribed input. METHOD: A subset of 11,999 archival responses produced on the Philadelphia Naming Test were classified into six cardinal paraphasia types using ParAlg under two transcription configurations: (a) using phonemic transcriptions for responses exclusively (phonemic-only) and (b) using phonemic transcriptions for nonlexical responses and orthographic transcriptions for lexical responses (orthographic-lexical). Agreement was quantified by comparing ParAlg-generated paraphasia codes between configurations and relative to human-annotated codes using four metrics (positive predictive value, sensitivity, specificity, and F1 score). An item-level qualitative analysis of misclassifications under the best performing configuration was also completed to identify the source and nature of coding discrepancies. RESULTS: Agreement between ParAlg-generated and human-annotated codes was high, although the orthographic-lexical configuration outperformed phonemic-only (weighted-average F1 scores of .78 and .87, respectively). A qualitative analysis of the orthographic-lexical configuration revealed a mix of human- and ParAlg-related misclassifications, the former of which were related primarily to phonological similarity judgments whereas the latter were due to semantic similarity assignment. CONCLUSIONS: ParAlg is an accurate and efficient alternative to manual scoring of paraphasias, particularly when lexical responses are orthographically transcribed. With further development, it has the potential to be a useful software application for anomia assessment. SUPPLEMENTAL MATERIAL: https://doi.org/10.23641/asha.22087763.

Refining Semantic Similarity of Paraphasias Using a Contextual Language Model.

PURPOSE: ParAlg (Paraphasia Algorithms) is a software that automatically categorizes a person with aphasia's naming error (paraphasia) in relation to its intended target on a picture-naming test. These classifications (based on lexicality as well as semantic, phonological, and morphological similarity to the target) are important for characterizing an individual's word-finding deficits or anomia. In this study, we applied a modern language model called BERT (Bidirectional Encoder Representations from Transformers) as a semantic classifier and evaluated its performance against ParAlg's original word2vec model. METHOD: We used a set of 11,999 paraphasias produced during the Philadelphia Naming Test. We trained ParAlg with word2vec or BERT and compared their performance to humans. Finally, we evaluated BERT's performance in terms of word-sense selection and conducted an item-level discrepancy analysis to identify which aspects of semantic similarity are most challenging to classify. RESULTS: Compared with word2vec, BERT qualitatively reduced word-sense issues and quantitatively reduced semantic classification errors by almost half. A large percentage of errors were attributable to semantic ambiguity. Of the possible semantic similarity subtypes, responses that were associated with or category coordinates of the intended target were most likely to be misclassified by both models and humans alike. CONCLUSIONS: BERT outperforms word2vec as a semantic classifier, partially due to its superior handling of polysemy. This work is an important step for further establishing ParAlg as an accurate assessment tool.

Computer Adaptive Testing for the Assessment of Anomia Severity.

Anomia assessment is a fundamental component of clinical practice and research inquiries involving individuals with aphasia, and confrontation naming tasks are among the most commonly used tools for quantifying anomia severity. While currently available confrontation naming tests possess many ideal properties, they are ultimately limited by the overarching psychometric framework they were developed within. Here, we discuss the challenges inherent to confrontation naming tests and present a modern alternative to test development called item response theory (IRT). Key concepts of IRT approaches are reviewed in relation to their relevance to aphasiology, highlighting the ability of IRT to create flexible and efficient tests that yield precise measurements of anomia severity. Empirical evidence from our research group on the application of IRT methods to a commonly used confrontation naming test is discussed, along with future avenues for test development.

Code-Switching and Language Proficiency in Bilingual Children With and Without Developmental Language Disorder.

Purpose This study examined the frequency of code-switching by Spanish-English-speaking children as a function of language proficiency in each language and diagnosis (developmental language disorder [DLD] or typical language development [TLD]). Method Sixty-two Spanish-English-speaking children, 5-7 years of age, participated in this study (24 with DLD and 38 with TLD). Language samples were used to determine the level of language proficiency in each language as a continuum of performance. Correlational analyses were conducted to evaluate the relationship between Spanish and English language proficiency and the frequency of code-switching considering the total number of code-switched words, intrasentential code-switching (i.e., number of sentences/C-units with code-switched parts), and intersentential code-switching (i.e., code-switched sentences/C-units). Negative binomial and zero-inflated Poisson regressions were conducted to evaluate whether the frequency of code-switched words, code-switched parts, and code-switched sentences is different across children with DLD and their peers with TLD, controlling for Spanish and English proficiency. Results When Spanish was the target language, lower proficiency in Spanish was associated with higher frequency of code-switches to English for the group with DLD, but not for their peers with TLD who code-switched to English regardless of their Spanish and English proficiency. There were no statistically significant effects of diagnosis on the frequency of code-switches. Conclusion Results indicate that code-switching occurs similarly across children with DLD and their peers with TLD; therefore, the frequency and type of code-switches should not be used as an indicator of DLD.

Effects of Phonomotor Therapy and Semantic Feature Analysis on Discourse Production.

Background Anomia treatments typically focus on single word retrieval, although the ultimate goal of treatment is to improve functional communication at the level of discourse in daily situations. Aims The focus of this study was to investigate the impact of two effective anomia treatments on discourse production as measured by a story retell task. Method and Procedure Fifty-seven people with aphasia were randomized to receive either a phoneme-based treatment, Phonomotor Therapy (PMT; 28 participants), or a lexical-semantic treatment, Semantic Feature Analysis (SFA; 29 participants). Groups were matched for age, aphasia severity, education, and years post onset. All received 56-60 hr of treatment in a massed treatment schedule. Therapy was delivered for a total of 8-10 hr/week over the course of 6-7 weeks. All participants completed testing 1 week prior to treatment (A1), immediately following treatment (A2), and again 3 months later (A3). Discourse was analyzed through the percentage of correct information units at each time point. Outcomes and Results Both groups showed nonsignificant improvements from pretreatment to immediately posttreatment. The PMT group showed significant improvement 3 months posttreatment, while the SFA group returned to near-baseline levels. Conclusion These results add to our understanding of the effects of both PMT and SFA. Future research should address understanding variability in discourse outcomes across studies and the effects of aphasia severity and individual participant and treatment factors on treatment outcomes for both of these approaches.

Empirical Evaluation of Computer-Adaptive Alternate Short Forms for the Assessment of Anomia Severity.

Purpose The purpose of this study was to verify the equivalence of 2 alternate test forms with nonoverlapping content generated by an item response theory (IRT)-based computer-adaptive test (CAT). The Philadelphia Naming Test (PNT; Roach, Schwartz, Martin, Grewal, & Brecher, 1996)was utilized as an item bank in a prospective, independent sample of persons with aphasia. Method Two alternate CAT short forms of the PNT were administered to a sample of 25 persons with aphasia who were at least 6 months postonset and received no treatment for 2 weeks before or during the study. The 1st session included administration of a 30-item PNT-CAT, and the 2nd session, conducted approximately 2 weeks later, included a variable-length PNT-CAT that excluded items administered in the 1st session and terminated when the modeled precision of the ability estimate was equal to or greater than the value obtained in the 1st session. The ability estimates were analyzed in a Bayesian framework. Results The 2 test versions correlated highly (r = .89) and obtained means and standard deviations that were not credibly different from one another. The correlation and error variance between the 2 test versions were well predicted by the IRT measurement model. Discussion The results suggest that IRT-based CAT alternate forms may be productively used in the assessment of anomia. IRT methods offer advantages for the efficient and sensitive measurement of change over time. Future work should consider the potential impact of differential item functioning due to person factors and intervention-specific effects, as well as expanding the item bank to maximize the clinical utility of the test. Supplemental Material https://doi.org/10.23641/asha.11368040.

Predicting confrontation naming item difficulty.

BACKGROUND: Item response theory (IRT; Lord & Novick, 1968) is a psychometric framework that can be used to model the likelihood that an individual will respond correctly to an item. Using archival data (Mirman et al., 2010), Fergadiotis, Kellough, and Hula (2015) estimated difficulty parameters for the Philadelphia Naming Test (PNT; Roach, Schwartz, Martin, Grewal, & Brecher, 1996) using the 1-parameter logistic IRT model. Although the use of IRT in test development is advantageous, its reliance on sample sizes exceeding 200 participants make it difficult to implement in aphasiology. Therefore, alternate means of estimating the item difficulty of confrontation naming test items warrant investigation. In a preliminary study aimed at automatic item calibration, Swiderski, Fergadiotis, and Hula (2016) regressed the difficulty parameters from the PNT on word length, age of acquisition (Kuperman et al., 2012), lexical frequency as quantified by the Log10CD index (Brysbaert & New, 2009), and naming latency (Székely et al., 2003). Although this model successfully explained a substantial proportion of variance in the PNT difficulty parameters, a substantial proportion (20%) of the response time data were missing. Further, only 39% of the picture stimuli from Székely and colleagues (2003) were identical to those on the PNT. Given that the IRT sample size requirements limit traditional calibration approaches in aphasiology and that the initial attempts in predicting IRT difficulty parameters in our pilot study were based on incomplete response time data this study has two specific aims. AIMS: To estimate naming latencies for the 175 items on the PNT, and assess the utility of psycholinguistic variables and naming latencies for predicting item difficulty. METHODS AND PROCEDURES: Using a speeded picture naming task we estimated mean naming latencies for the 175 items of the Philadelphia Naming test in 44 cognitively healthy adults. We then re-estimated the model reported by Swiderski et al (2016) with the new naming latency data. RESULTS: The predictor variables described above accounted for a substantial proportion of the variance in the item difficulty parameters (Adj. R 2 = .692). CONCLUSIONS: In this study we demonstrated that word length, age of acquisition, lexical frequency, and naming latency from neurotypical young adults usefully predict picture naming item difficulty in people with aphasia. These variables are readily available or easily obtained and the regression model reported may be useful for estimating confrontation naming item difficulty without the need for collection of response data from large samples of people with aphasia.

Enhancing the Efficiency of Confrontation Naming Assessment for Aphasia Using Computer Adaptive Testing.

Purpose In this study, we investigated the agreement between the 175-item Philadelphia Naming Test (PNT; Roach, Schwartz, Martin, Grewal, & Brecher, 1996 ) and a 30-item computer adaptive PNT (PNT-CAT; Fergadiotis, Kellough, & Hula, 2015 ; Hula, Kellough, & Fergadiotis, 2015 ) created using item response theory (IRT) methods. Method The full PNT and the PNT-CAT were administered to 47 participants with aphasia in counterbalanced order. Latent trait-naming ability estimates for the 2 PNT versions were analyzed in a Bayesian framework, and the agreement between them was evaluated using correlation and measures of constant, variable, and total error. We also evaluated the extent to which individual pairwise differences were credibly greater than 0 and whether the IRT measurement model provided an adequate indication of the precision of individual score estimates. Results The agreement between the PNT and the PNT-CAT was strong, as indicated by high correlation ( r = .95, 95% CI [.92, .97]), negligible bias, and low variable and total error. The number of statistically robust pairwise score differences did not credibly exceed the Type I error rate, and the precision of individual score estimates was reasonably well predicted by the IRT model. Discussion The strong agreement between the full PNT and the PNT-CAT suggests that the latter is a suitable measurement of anomia in group studies. The relatively robust estimates of score precision also suggest that the PNT-CAT can be useful for the clinical assessment of anomia in individual cases. Finally, the IRT methods used to construct the PNT-CAT provide a framework for additional development to further reduce measurement error. Supplemental Material https://doi.org/10.23641/asha.8202176.

Effects of Phonomotor Treatment on discourse production.

BACKGROUND: Aphasia is an acquired language disorder that makes it difficult for people to produce and comprehend language, with every person with aphasia (PWA) demonstrating difficulty accessing and selecting words (anomia). While aphasia treatments typically focus on a single aspect of language, such as word retrieval, the ultimate goal of aphasia therapy is to improve communication, which is best seen at the level of discourse. AIMS: This retrospective study investigated the effects of one effective anomia therapy, Phonomotor Treatment, on discourse production. METHODS & PROCEDURES: Twenty-six PWA participated in 60 hours of Phonomotor Treatment, which focuses on building a person's ability to recognise, produce, and manipulate phonemes in progressively longer non-word and real-word contexts. Language samples were collected prior to, immediately after, and three months after the treatment program. Percent Correct Information Units (CIUs) and CIUs per minute were calculated. OUTCOMES & RESULTS: Overall, PWA showed significantly improved CIUs per minute, relative to baseline, immediately after treatment and three months later, as well as significantly improved percent CIUs, relative to baseline, three months following treatment. CONCLUSIONS: Phonomotor Treatment, which focuses on phonological processing, can lead to widespread improvement throughout the language system, including to the functionally critical level of discourse production.

Psychometric Evaluation of Lexical Diversity Indices in Spanish Narrative Samples From Children With and Without Developmental Language Disorder.

Purpose The purpose of the current study was to examine construct validity evidence for the following 4 lexical diversity measures for use in Spanish narrative samples of children with developmental language disorder and typical language development (TLD): (a) type-token ratio (TTR; Chotlos, 1944 ; Templin, 1957 ), (b) hypergeometric distribution D ( McCarthy & Jarvis, 2010 ), (c) measure of textual lexical diversity (MTLD; McCarthy, 2005 ), and (d) moving-average TTR (MATTR; Covington & McFall, 2010 ). Method A multiple-group, confirmatory factor analytic stepwise procedure was applied to examine factorial invariance in a sample of 435 monolingual Spanish-speaking children (335 with TLD and 100 with specific language impairment). Results MATTR was the strongest indicator of the lexical diversity of a sample and demonstrated measurement invariance across children with TLD and specific language impairment. MTLD scores included some noise at different levels as a function of the length of a sample, especially for short language samples, but differences in relation to MATTR were relatively small. The validity of hypergeometric distribution D and TTR score interpretations was low, as the scores covaried systematically with length, with TTR being the poorest measure of lexical diversity. Conclusion Results support the use of MATTR and MTLD as measures of lexical diversity and should assist clinicians and researchers in the selection of lexical diversity measures to minimize bias in score interpretations when conducting language sample analyses.

Language Sample Analysis and Elicitation Technique Effects in Bilingual Children With and Without Language Impairment.

Purpose: This study examined whether the language sample elicitation technique (i.e., storytelling and story-retelling tasks with pictorial support) affects lexical diversity (D), grammaticality (grammatical errors per communication unit [GE/CU]), sentence length (mean length of utterance in words [MLUw]), and sentence complexity (subordination index [SI]), which are commonly used indices for diagnosing primary language impairment in Spanish-English-speaking children in the United States. Method: Twenty bilingual Spanish-English-speaking children with typical language development and 20 with primary language impairment participated in the study. Four analyses of variance were conducted to evaluate the effect of language elicitation technique and group on D, GE/CU, MLUw, and SI. Also, 2 discriminant analyses were conducted to assess which indices were more effective for story retelling and storytelling and their classification accuracy across elicitation techniques. Results: D, MLUw, and SI were influenced by the type of elicitation technique, but GE/CU was not. The classification accuracy of language sample analysis was greater in story retelling than in storytelling, with GE/CU and D being useful indicators of language abilities in story retelling and GE/CU and SI in storytelling. Conclusion: Two indices in language sample analysis may be sufficient for diagnosis in 4- to 5-year-old bilingual Spanish-English-speaking children.

Algorithmic Classification of Five Characteristic Types of Paraphasias.

Purpose: This study was intended to evaluate a series of algorithms developed to perform automatic classification of paraphasic errors (formal, semantic, mixed, neologistic, and unrelated errors). Method: We analyzed 7,111 paraphasias from the Moss Aphasia Psycholinguistics Project Database (Mirman et al., 2010) and evaluated the classification accuracy of 3 automated tools. First, we used frequency norms from the SUBTLEXus database (Brysbaert & New, 2009) to differentiate nonword errors and real-word productions. Then we implemented a phonological-similarity algorithm to identify phonologically related real-word errors. Last, we assessed the performance of a semantic-similarity criterion that was based on word2vec (Mikolov, Yih, & Zweig, 2013). Results: Overall, the algorithmic classification replicated human scoring for the major categories of paraphasias studied with high accuracy. The tool that was based on the SUBTLEXus frequency norms was more than 97% accurate in making lexicality judgments. The phonological-similarity criterion was approximately 91% accurate, and the overall classification accuracy of the semantic classifier ranged from 86% to 90%. Conclusion: Overall, the results highlight the potential of tools from the field of natural language processing for the development of highly reliable, cost-effective diagnostic tools suitable for collecting high-quality measurement data for research and clinical purposes.

Semantic Knowledge Use in Discourse Produced by Individuals with Anomic Aphasia.

BACKGROUND: Researchers have demonstrated that people with aphasia (PWA) have preserved semantic knowledge (Dell et al., 1997; Jefferies & Lambon Ralph, 2006). However, Antonucci (2014) demonstrated that some PWA have impaired access to certain types of knowledge more than others. Yet, all these studies used single concepts. It has not been demonstrated whether PWA have difficulty accessing certain types of features within a discourse sample. AIMS: The main goals of this study were to determine if semantic knowledge and two category types were used differently within discourse produced by participants with anomic aphasia and healthy controls. METHOD & PROCEDURES: Participants with anomic aphasia (n=19) and healthy controls (n=19) told stories that were transcribed and coded for 10 types of semantic knowledge and two category types, living and nonliving things. OUTCOMES & RESULTS: A Poisson regression model was conducted. The results indicated a significant difference between the groups for the semantic knowledge types, sound and internal state, but no difference was found for category types. Yet the distribution of semantic knowledge and category types produced within the discourse samples were similar between the groups. CONCLUSION: PWA might have differential access to certain types of semantic knowledge within discourse production, but it does not rise to the level of categorical deficits. These findings extend single-concept research into the realm of discourse.

Item Response Theory Modeling of the Philadelphia Naming Test.

PURPOSE: In this study, we investigated the fit of the Philadelphia Naming Test (PNT; Roach, Schwartz, Martin, Grewal, & Brecher, 1996) to an item-response-theory measurement model, estimated the precision of the resulting scores and item parameters, and provided a theoretical rationale for the interpretation of PNT overall scores by relating explanatory variables to item difficulty. This article describes the statistical model underlying the computer adaptive PNT presented in a companion article (Hula, Kellough, & Fergadiotis, 2015). METHOD: Using archival data, we evaluated the fit of the PNT to 1- and 2-parameter logistic models and examined the precision of the resulting parameter estimates. We regressed the item difficulty estimates on three predictor variables: word length, age of acquisition, and contextual diversity. RESULTS: The 2-parameter logistic model demonstrated marginally better fit, but the fit of the 1-parameter logistic model was adequate. Precision was excellent for both person ability and item difficulty estimates. Word length, age of acquisition, and contextual diversity all independently contributed to variance in item difficulty. CONCLUSIONS: Item-response-theory methods can be productively used to analyze and quantify anomia severity in aphasia. Regression of item difficulty on lexical variables supported the validity of the PNT and interpretation of anomia severity scores in the context of current word-finding models.

Development and Simulation Testing of a Computerized Adaptive Version of the Philadelphia Naming Test.

PURPOSE: The purpose of this study was to develop a computerized adaptive test (CAT) version of the Philadelphia Naming Test (PNT; Roach, Schwartz, Martin, Grewal, & Brecher, 1996), to reduce test length while maximizing measurement precision. This article is a direct extension of a companion article (Fergadiotis, Kellough, & Hula, 2015), in which we fitted the PNT to a 1-parameter logistic item-response-theory model and examined the validity and precision of the resulting item parameter and ability score estimates. METHOD: Using archival data collected from participants with aphasia, we simulated two PNT-CAT versions and two previously published static PNT short forms, and compared the resulting ability score estimates to estimates obtained from the full 175-item PNT. We used a jackknife procedure to maintain independence of the samples used for item estimation and CAT simulation. RESULTS: The PNT-CAT recovered full PNT scores with equal or better accuracy than the static short forms. Measurement precision was also greater for the PNT-CAT than the static short forms, though comparison of adaptive and static nonoverlapping alternate forms showed minimal differences between the two approaches. CONCLUSION: These results suggest that CAT assessment of naming in aphasia has the potential to reduce test burden while maximizing the accuracy and precision of score estimates.