Objective

This retrospective study investigated the effect of processing speed on confrontation naming performance via five naming tests with varying time components.

Method

The effect of processing speed, as measured by the Wechsler Adult Intelligence Scale-Fourth Edition Processing Speed Index (PSI), and cognitive impairment were examined using Boston Naming Test, Neuropsychological Assessment Battery Naming Test, Visual Naming Test (VNT), Auditory Naming Test (ANT), and Woodcock-Johnson III Rapid Picture Naming (RPN) performance among a mixed clinical sample of 115 outpatient veterans.

Results

PSI scores accounted for 5%–26% of the total variance in naming test performances. Comparison of cognitively impaired versus unimpaired participants found significant differences and medium to large effect sizes (η2 = .08–.20) for all naming measures except ANT tip-of-the-tongue responses. After controlling for the effect processing speed, VNT tip-of-the-tongue responses also became non-significant, whereas significant group differences remained present for all other naming test scores, albeit with notably smaller effects sizes (η2 = .06–.10).

Conclusions

Confrontation naming test performance is related to cognitive processing speed, although the magnitude of this effect varies by the demands of each naming test (i.e., largest for RPN; smallest for VNT). Thus, results argue that processing speed is important to consider for accurate clinical interpretation of naming tests, especially in the context of cognitive impairment.

Introduction

Confrontation naming tests are nearly ubiquitous for assessing language function, and more specifically, word-finding ability, in neuropsychological evaluations. Despite the deceptively simple premise of naming tests, intact performance on these measures is contingent upon a complex array of neuroanatomical systems and cognitive processes, including visual-perceptual processing, the activation and search of sematic-lexical networks, conceptual representation, and phonological output (Dell, Schwartz, Martin, Saffran, & Gagnon, 1997; Schwartz, 2014; Soble et al., 2016). Although not often stated directly in many models, processing speed also can be considered as an inherent component in the naming process.

The construct of processing speed has been diversely conceptualized in the literature (e.g., perceptual speed, psychomotor speed, and reaction time). DeLuca (2008) broadly operationalized processing speed as “either the time required to execute a cognitive task or the amount of work that can be completed within a finite period of time” (p. 266). Further distinction has been drawn between simple processing speed (i.e., basic reaction time tasks) and complex speed tasks requiring more mental exertion (e.g., Paced Auditory Serial Addition Test; Chiaravalloti, Christodoulou, Demaree, & DeLuca, 2003). Though somewhat broad, it can be argued this operational definition adequately portrays the ubiquitous nature of processing speed and highlights that this domain warrants consideration while assessing nearly all other domains of cognitive functioning. Notably, an abundance of common neuropsychological measures contains a processing speed feature as either a primary measure or a secondary test property. Tasks in which processing speed is primary are those for which the speed at which the task can be completed is the main performance variable of interest (e.g., Trail Making Test Part A; Reitan & Wolfson, 1993), or those for which participants must complete as many items as possible in a fixed time (e.g., Stroop Color Word Test; Golden, 1978). Measures for which processing speed is secondary are those that require participants to provide a correct response within a specified time limit (e.g., Visual Puzzles and Block Design on the Wechsler Adult Intelligence Scale-Fourth Edition, WAIS-IV; Wechsler, 2008a). Most confrontation naming tests, such as the Boston Naming Test (BNT; Kaplan, Goodglass, & Weintraub, 1983) and Neuropsychological Assessment Battery (NAB) Naming Test (Stern & White, 2009), similarly include processing speed as a secondary aspect of item administration in the form of time limits (i.e., 10–20 s) in which examinees must produce a correct response. Moreover, there are some naming measures in which processing speed is a primary component of the test, such as the Rapid Picture Naming (RPN) subtest from the Woodcock-Johnson III Test of Cognitive Abilities (WJ-III; Woodcock, McGrew, & Mather, 2001).

Even with the underlying time requirements inherent to most naming tests, the relationship between processing speed and confrontation naming assessment remains incompletely explored. Among children, processing speed was found to significantly predict naming time for familiar stimuli and speed deficits were associated with difficulty in rapid object naming (Catts, Gillispie, Leonard, Kail, & Miller, 2002; Kail, Hall, & Caskey, 1999). Studies with adults found declines in confrontation naming performance were associated with normal aging (Connor, Spiro, Obler, & Albert, 2004; Gutherie et al., 2010) and related to response latency (Tsang & Lee, 2003). Also, processing speed has been noted to be particularly sensitive to normal aging due to changes in both gray and white matter, which can degrade overall cognitive performance across multiple tasks (Eckert, Keren, Roberts, Calhoun, & Harris, 2010; Kerchner et al., 2012; Salthouse, 1996).

Given the previous findings and limited available data, the purpose of this study was to investigate the effect of processing speed on naming performance among a mixed clinical sample of adults by examining five naming measures with varying time components: the BNT (Kaplan et al., 1983), NAB Naming Test (Stern & White, 2009), Visual Naming Test (VNT; Hamberger & Seidel, 2003), Auditory Naming Test (ANT; Hamberger & Seidel, 2003), and the RPN subtest (Woodcock et al., 2001). In addition to determining the effect of speed on naming performance, a secondary objective was to assess which naming measure(s) were able to differentiate participants with and without cognitive impairment after controlling for the effect of processing speed.

Materials and Methods

Participants

Data for this retrospective cross-sectional study were obtained from a mixed clinical sample of veterans who received comprehensive outpatient neuropsychological evaluation services from 2011 to 2015 at a VA medical center. Data were collected as part of a larger research project approved by the local Institutional Review Board, and all participants provided written informed consent prior to joining the study. Participants who completed the subtests needed to calculate the WAIS-IV PSI and selected naming measures were eligible for inclusion. Of the 125 who met the initial inclusion criteria, 10 were excluded due to poor performance on formal performance validity tests and concurrent clinical evidence of invalid performance, which resulted in a final sample size of 115. The majority of participants were men (N = 100; 87%). The sample was 53% Caucasian (N = 61), 35% Hispanic (N = 40), 10% African American (N = 11), and 2% Other (N = 3). Twenty-nine percent (N = 33) of the sample was bilingual with no significant group differences between bilinguals and monolinguals present in terms of cognitive impairment status (i.e., intact versus impaired), X2 (1, N = 115) = 2.37, p =.12, or severity of cognitive impairment (i.e., intact, mild neurocognitive disorder, major neurocognitive disorder), X2 (2, N = 115) = 2.39, p = .30. Mean age was 58.75 years (SD = 12.2) and participants completed an average of 13.1 years (SD = 3.0) of formal education. Thirty-eight percent (N = 44) was cognitively intact and 62% (N = 71) met criteria for a neurocognitive disorder. All neurocognitive disorder diagnoses were clinical diagnoses established at the time of each participant's neuropsychological evaluation according to formal Diagnostic and Statistical Manual of Mental Disorders-Fifth Edition (DSM-5; APA, 2013) diagnostic criteria. Of the 71 cognitively impaired, 76% (N = 54) met DSM-5 criteria for a mild neurocognitive disorder and 24% (N = 17) met criteria for a major neurocognitive disorder. Vascular etiologies were most common (N = 21; 30%) with the remainder of the sample having diagnoses of amnestic subtype-mild cognitive impairment (N = 6; 8%), multiple sclerosis (N = 4; 6%), other medical and neurological conditions (N = 11; 15%), multiple etiologies (N = 18; 25%), attention-deficit/hyperactivity disorder (N = 2; 3%), or an unspecified etiology (N = 9; 13%). Finally, due to a change in clinic procedures, only 60 of the 115 total participants were administered the RPN subtest. Of these 60, 37% were cognitively intact (N = 22) and 63% were cognitively impaired (N = 38). There were no significant demographic differences between those who were and were not administered the RPN subtest in terms of age and education, Wilks's Λ = 1.00, F(2, 112) = .22, p = .98, η2 = .000; race, X2 (3, N = 115) = 4.95, p = .18; or cognitive impairment status, X2 (1, N = 115) = .14, p = . 71.

Measures

As part of the clinical battery and protocol for a larger, ongoing naming study, participants were administered the BNT, NAB Naming Test, VNT, ANT, RPN, and WAIS-IV. In order to control for order effects, naming measures were counterbalanced.

Boston Naming Test

The BNT (Kaplan et al., 1983) is a measure of confrontation naming, in which participants are asked to provide the names of up to 60 line-drawn pictures with increasing difficulty. Following standard administration instructions, the pictures were presented in order, beginning with item 30, until the discontinue rule of eight consecutive errors was reached. Participants were given up to 20 s to provide their initial response and standard administration was followed regarding the provision of stimulus and phonemic cues. The BNT total score was used; total score comprises initially-correct responses and correct responses following stimulus cues.

NAB Naming Test

The NAB Naming Test (Stern & White, 2009) is a measure of confrontation naming, in which participants are asked to provide the names of 31 color photographed items with increasing difficulty. All items were administered in order, beginning with item 1. Following standard administration instructions, participants were given 10 s to respond. No response or incorrect responses were followed by a semantic cue, after which they were given 5 s to respond. No response or incorrect responses following the semantic cue were followed by a phonemic cue, after which the examinees were given 5 s to respond. The total score comprises the total number correct prior to any cues.

Visual Naming Test

Similar to the BNT, the VNT (Hamberger & Seidel, 2003) is a measure of confrontation naming, which requires participants to provide the names of 50 line-drawn pictures “as quickly as possible”; however, these pictures do not increase in difficulty. All items were administered in order, beginning with item 1. Although the participants were given 20 s in which to provide a correct response, if an incorrect response is given, they were asked to provide an additional response (i.e., “What else?”) during the 20 s. If they did not provide a correct response within the 20 s, they were provided with a phonemic cue and given 5 s to respond. The total score comprises all correct responses within 20 s. A separate score is also calculated for tip-of-the-tongue responses. Tip-of-the-tongue responses are defined as initially-correct responses given after 2 s but within 20 s and correct responses given after a phonemic cue.

Auditory Naming Test

The ANT (Hamberger & Seidel, 2003) is a measure of auditory word finding, which requires participants to provide the name of 50 items that are described by a short phrase “as quickly as possible.” These phrases do not increase in their level of difficulty. For example, a participant would be asked to say, “dog” when told, “A four-legged animal that barks.” Administration and scoring instructions for the ANT are exactly the same as those for the VNT.

Rapid Picture Naming

Rapid Picture Naming subtest of the Woodcock-Johnson III Tests of Cognitive Abilities (Woodcock et al., 2001) is a measure of speeded naming, in which participants are presented with 120 line-drawn, common objects and asked to name them “as fast as you can.” No cues or feedback are given. The test is discontinued when the participants complete all items or when the 120-s time limit expires. The RPN total score is derived from the number of correct responses within the 120-s time limit.

WAIS-IV Processing Speed Index

The Processing Speed Index (PSI) of the WAIS-IV (Wechsler, 2008a) is a standard score derived from a participant's performance on the Coding and Symbol Search subtests. Although the Cancellation subtest may be used to calculate PSI, all participants in this study were given the Coding and Symbol Search subtests. According to the WAIS-IV Technical and Interpretive Manual (Wechsler, 2008b), the PSI provides “a measure of the examinee's ability to quickly and correctly scan, sequence, or discriminate simple visual information” (p. 129). The Coding subtest requires participants to copy symbols from a key containing paired numbers and symbols; they are asked to complete the task “as fast as you can without making mistakes” within a 120-s time limit. The Symbol Search subtest requires participants to scan an array for symbols matching a target. Again, they are given 120 s and asked to work “as fast as you can without making mistakes.”

Data Analysis

Descriptive statistics and correlations were calculated for the primary clinical variables. In order to test the effect of processing speed on naming performance, a series of linear regression analyses were conducted with PSI entered as the predictor variable and a naming measure as the outcome variable in each model. Next, a multivariate analysis of variance (MANOVA) was performed with cognitive impairment status (i.e., cognitively intact or impaired) entered as the fixed factor and the naming measures (i.e., BNT, VNT, ANT, and NAB) as the dependent variables. Based on the significant MANOVA, follow-up univariate analyses of variance (ANOVAs) were examined. Finally, a multivariate analysis of covariance (MANCOVA) with follow-up univariate analyses of covariance (ANCOVAs) was conducted with cognitive impairment status as the fixed factor, processing speed (i.e., PSI) as the covariate, and the naming measures as the dependent variables to determine whether performance on any of the naming measures remained significantly different between those with and without cognitive impairment after controlling for processing speed. Because only a subset of 60 participants had RPN scores, this subtest was evaluated separately via a univariate ANCOVA with cognitive impairment entered as the fixed factor, PSI as the covariate, and RPN as the dependent variable. To address the issue of multiple post hoc comparisons in the multivariate analyses, the false discovery rate (FDR) procedure was implemented using a 0.05 maximum FDR in order to control the false positive rate while also maximizing power (Benjamini & Hochberg, 1995; Glickman, Rao, & Schultz, 2014).

Results

Means, standard deviations, and correlation coefficients for the primary clinical variables are presented in Table 1. As anticipated, the naming measures were significantly correlated with each other, although it was noted also that PSI was significantly correlated with each naming measure, with the strongest correlation between PSI and RPN.

Table 1.

Correlations between primary clinical measures

 M (SD) BNT NAB VNT VNTt ANT ANTt RPN 
PSI 88.37 (14.0) .31** .26** .22* −.31** .31** −.26** .51** 
BNT 51.73 (6.5) — .76** .65** −.51** .80** −.44** .55** 
NAB 29.24 (2.4)  — .69** −.66** .77** −.48** .54** 
VNT 49.19 (1.4)   — −.61** .66** −.38** .44** 
VNTt 2.03 (2.4)    — −.52** .51** −.36** 
ANT 46.52 (4.0)     — −.55** .48** 
ANTt 7.79 (5.8)      — −.33* 
RPN 97.35 (21.9)       — 
 M (SD) BNT NAB VNT VNTt ANT ANTt RPN 
PSI 88.37 (14.0) .31** .26** .22* −.31** .31** −.26** .51** 
BNT 51.73 (6.5) — .76** .65** −.51** .80** −.44** .55** 
NAB 29.24 (2.4)  — .69** −.66** .77** −.48** .54** 
VNT 49.19 (1.4)   — −.61** .66** −.38** .44** 
VNTt 2.03 (2.4)    — −.52** .51** −.36** 
ANT 46.52 (4.0)     — −.55** .48** 
ANTt 7.79 (5.8)      — −.33* 
RPN 97.35 (21.9)       — 

Note: PSI = Wechsler Adult Intelligence Scale-Fourth Edition (WAIS-IV) Processing Speed Index (Standard Score); BNT = Boston Naming Test (raw score); NAB = Neuropsychological Assessment Battery Naming Test (raw score); VNT = Visual Naming Test (raw score); VNTt = Visual Naming Test-tip of the tongue (raw score); ANT = Auditory Naming Test (raw Score); ANTt = Auditory Naming Test-tip of the tongue (raw score); RPN = Woodcock-Johnson III Test of Cognitive Abilities (WJ-III) Rapid Picture Naming subtest (raw score). N = 115 for all variables except RPN (N = 60). *p < .05, **p < .01.

The linear regression models revealed that PSI was a significant predictor for all of the naming measures and accounted for 10% of the total variance in BNT scores, 7% in NAB scores, 5% in VNT scores, 9% in VNT tip-of-the-tongue scores, 10% in ANT scores, 7% in ANT tip-of-the-tongue scores, and 26% in RPN scores (see Table 2).

Table 2.

Regression models

Model R2 Model F B SE B β t 
PSI → BNT .10 12.10** .14 .04 .31 3.47** 
PSI → NAB .07 8.22** .04 .02 .26 2.87** 
PSI → VNT .05 5.48* .02 .01 .22 2.34* 
PSI → VNTt .09 11.68** −.05 .02 −.31 −3.42** 
PSI → ANT .10 12.20** .09 .03 .31 3.49** 
PSI → ANTt .07 7.96** −.11 .04 −.26 −2.82** 
PSI → RPN .26 19.97*** .74 .17 .51 4.47*** 
Model R2 Model F B SE B β t 
PSI → BNT .10 12.10** .14 .04 .31 3.47** 
PSI → NAB .07 8.22** .04 .02 .26 2.87** 
PSI → VNT .05 5.48* .02 .01 .22 2.34* 
PSI → VNTt .09 11.68** −.05 .02 −.31 −3.42** 
PSI → ANT .10 12.20** .09 .03 .31 3.49** 
PSI → ANTt .07 7.96** −.11 .04 −.26 −2.82** 
PSI → RPN .26 19.97*** .74 .17 .51 4.47*** 

Note: PSI = Wechsler Adult Intelligence Scale-Fourth Edition (WAIS-IV) Processing Speed Index; BNT = Boston Naming Test; NAB = Neuropsychological Assessment Battery Naming Test; VNT = Visual Naming Test; VNTt = Visual Naming Test-tip of the tongue; ANT = Auditory Naming Test; ANTt = Auditory Naming Test-tip of the tongue; RPN = Woodcock-Johnson Test of Cognitive Abilities III (WJ-III) Rapid Picture Naming subtest. N = 115 for all variables except RPN (N = 60). *p < .05, **p < .01, ***p < .001.

The MANOVA with cognitive impairment status as the fixed factor and the naming measures as the dependent variables was significant overall, Wilks's Λ = .80, F(6, 108) = 4.64, p < .001, η2 = .21. As noted in Table 3, follow-up ANOVAs revealed scores on all of the naming measures were significantly lower for the cognitively impaired group relative to those without cognitive impairment except for ANT tip-of-the-tongue scores. A separate univariate ANOVA with cognitive impairment as the fixed factor and RPN scores as the dependent variable showed significantly worse performance among the cognitively impaired group, F(1, 58) = 14.74, p < .01, η2 = .20. In order to control for the effect of processing speed, a MANCOVA was conducted with cognitive impairment status as the fixed factor, PSI as the covariate, and naming scores as the dependent variables. The overall model again was significant, Wilks's Λ = .85, F(6, 107) = 3.19, p < .01, η2 = .15. Follow-up ANCOVAs indicated BNT, NAB, VNT, and ANT remained significantly different between groups after controlling for processing speed, albeit with smaller effect sizes that were roughly half as large. VNT tip-of-the-tongue scores were significant no longer and the effect size for the previous non-significant ANT tip-of-the-tongue scores decreased further to near-zero. Likewise, a univariate ANCOVA with RPN revealed this measure continued to differ significantly after co-varying processing speed, but, again, with a considerable decrease in effect size, F(1, 57) = 4.70, p < .05, η2 = .08.

Table 3.

Comparisons between primary clinical measures

 Unimpaired, N = 44 Impaired, N = 71 F η2 PSI covaried 
M (SD) M (SD) F η2 
PSI 97.50 (11.5) 82.70 (12.4) 40.8*** .27 — — 
BNT 55.20 (4.1) 49.58 (6.8) 24.6*** .18 13.0** .10 
NAB 30.41 (0.79) 28.52 (2.7) 19.7*** .15 11.4** .09 
VNT 49.80 (0.46) 48.82 (1.7) 14.7** .12 9.0** .08 
VNTt 1.20 (1.6) 2.55 (2.6) 9.5** .08 2.5 .02 
ANT 48.39 (2.1) 45.37 (4.5) 17.3*** .13 7.5* .06 
ANTt 6.91 (6.1) 8.34 (5.6) 1.7 .01 .02 .000 
RPN 110.20 (11.5) 89.89 (23.2) 14.7** .20 4.7* .08 
 Unimpaired, N = 44 Impaired, N = 71 F η2 PSI covaried 
M (SD) M (SD) F η2 
PSI 97.50 (11.5) 82.70 (12.4) 40.8*** .27 — — 
BNT 55.20 (4.1) 49.58 (6.8) 24.6*** .18 13.0** .10 
NAB 30.41 (0.79) 28.52 (2.7) 19.7*** .15 11.4** .09 
VNT 49.80 (0.46) 48.82 (1.7) 14.7** .12 9.0** .08 
VNTt 1.20 (1.6) 2.55 (2.6) 9.5** .08 2.5 .02 
ANT 48.39 (2.1) 45.37 (4.5) 17.3*** .13 7.5* .06 
ANTt 6.91 (6.1) 8.34 (5.6) 1.7 .01 .02 .000 
RPN 110.20 (11.5) 89.89 (23.2) 14.7** .20 4.7* .08 

Note: PSI = Wechsler Adult Intelligence Scale-Fourth Edition (WAIS-IV) Processing Speed Index (Standard Score); BNT = Boston Naming Test (raw score); NAB = Neuropsychological Assessment Battery Naming Test (raw score); VNT = Visual Naming Test (raw score); VNTt = Visual Naming Test-tip of the tongue (raw score); ANT = Auditory Naming Test (raw Score); ANTt = Auditory Naming Test-tip of the tongue (raw score); RPN = Woodcock-Johnson III Test of Cognitive Abilities (WJ-III) Rapid Picture Naming subtest (raw score). N = 115 for all variables except RPN (N = 60). *p < .05, **p < .01, ***p < .001. All p-values reflect false discovery rate (FDR)-corrected p-values.

Discussion

This study investigated both the effect of processing speed on task variability in five naming tests and the utility of each naming measure in differentiating cognitively impaired and unimpaired groups after controlling for processing speed. Results indicated that processing speed has a significant effect on naming abilities and should be accounted for when interpreting confrontation naming test performances. Primary scores on the naming measures (i.e., total of correctly-named items) retained their ability to differentiate between cognitively impaired and normal groups after controlling for processing speed; however, there was a significant reduction in the magnitude of group differences once the effects of processing speed were minimized. This link between processing speed and naming ability has been demonstrated in a previous factor analytic study of Chinese participants. He and coworkers (2013) found that rapid color and object naming and Chinese sight word efficiency loaded with simple response times and WAIS-R FSIQ onto a single factor, which correlated with distributed gray-matter volume on MRI. The present study similarly found a significant relationship between speed and naming performance using several neuropsychological measures of confrontation naming and processing speed administered in English.

While processing speed affected naming performance across measures, the naming tests varied in their susceptibility to the effects of processing speed, which has implications for the selection and interpretation of naming test results. The strongest overall relationship existed between the WAIS-IV PSI and the RPN subtest, with processing speed accounting for 26% of the total variance in scores on this test (compared with the 5%–10% across other measures), such that the effect size notably decreased after controlling for speed, but still remained significant. This finding may relate to the nature of the tests themselves. Specifically, the BNT, VNT, ANT, and NAB naming test all include processing speed as a secondary aspect in the form of time limits related to individual stimuli (i.e., 10–20 s), whereas the RPN subtest measures sustained rapidity of responses across a 2-min period. A conceptual distinction between single item reaction time and sustained rapidity of response tasks has been argued, as sustained response tasks are more closely related to working memory and executive abilities than single item response speed tasks (Chiaravalloti et al., 2003). Some of the shared variance between the PSI and RPN may be due to the similar characteristics in the administration of those tasks, especially the requirement of sustained rapid responding over the course of 2 min, and task demands that overlap in their use of executive abilities such as sustained attention and shifting. For instance, factor analyses with the Woodcock-Johnson battery have shown that RPN and executive verbal fluency tasks load onto the same speed of lexical access factor (McGrew, LaForte, & Schrank, 2014). Thus, because of this robust relationship between speed and RPN, and the shared executive functioning demands between RPN and some processing speed tasks, the RPN subtest may not be the most appropriate test for assessing naming abilities when there are suspected impairments in executive functioning or processing speed. That being said, a comparison between performance on a naming test which includes processing speed as a primary component and one, or more, which incorporate processing speed as secondary aspect may prove useful in explaining word-finding complaints in patients with reduced processing speed and cognitive efficiency. In contrast to the RPN, processing speed had the smallest relationship with VNT performance, suggesting that this measure potentially may provide a more distinct representation of naming ability in the context of processing speed difficulties.

Results also revealed small-magnitude differences in the relationship between PSI and overall performance for BNT, NAB, ANT, and VNT, suggesting that the characteristics of the stimuli (i.e., auditory, color photographs and line drawings) were not primarily driving our findings, although a relationship between stimuli characteristics and processing speed has been noted in previous studies (Rogalski, Peele, & Reilly, 2011). The ANT and VNT also include a second method of response time scoring, with the tip-of-the-tongue measures purported to capture reduced naming efficiency and automaticity. Results showed that the ANT tip-of-the-tongue scores did not differ based on cognitive impairment status, regardless of processing speed, and that the VNT tip-of-the tongue scores no longer differentiated groups after controlling for processing speed variance such that the utility of these scores among those with reduced speed remains unclear. Nonetheless, these variables still may accurately capture subjective complaints of word-finding difficulties in conversation (Hamberger & Seidel, 2003).

There were several limitations to the current study. The mixed clinical sample of veterans was referred for neuropsychological evaluation; thus, the cognitively unimpaired group was a clinically-presenting group with subjective cognitive complaints. One additional limitation with the cognitively impaired group includes criterion contamination, as naming test scores were likely used as part of the broader test battery to identify impairment in many cases. Furthermore, the retrospective nature of the study limits generalizability of these results, as does the sampling bias inherent in conducting research within a clinical population. Future research prospectively investigating the relationships between processing speed and confrontation naming from a randomly selected sample and a matched control group would help establish the generalizability of these results. In addition, research examining alternative measures of the construct of processing speed, such as reaction time measures or simpler processing speed measures (e.g., Trail Making Test Part A), may help further establish the strength of the relationship between naming ability and cognitive speed.

Conclusion

In summary, this study revealed processing speed performance accounts for a significant portion of the variance among five naming tests, although each measure continued to provide unique information differentiating between cognitively impaired and unimpaired groups after controlling for processing speed. The strength of this speed-naming relationship suggests that some measures have advantages for assessment of naming ability, and that the impact of processing speed on naming test performance is an important consideration for accurate neuropsychological interpretation.

Funding

The authors have no financial interest with the subject matter discussed in the manuscript. The views expressed herein are those of the authors and do not necessarily reflect the views or the official policy of the Department of Veterans Affairs or U.S. Government.

Conflict of Interest

None declared.

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