Early naming deficits, developmental dyslexia, and a specific deficit hypothesis

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42, 219-247 (1992)

Early Naming Deficits, Developmental Dyslexia, and a Specific Deficit Hypothesis MARYANNE WOLF Tufts University AND MATEO OBREG~N Tufts University The present research represents the final 2 years of a S-year longitudinal investigation of (a) confrontation-based, word-retrieval deficits in dyslexic children; (b) the role of vocabulary development in these deficits; (c) the relationship between confrontation naming performance and three carefully defined aspects of reading performance in the general population and in eight dyslexic case studies; and (d) the possible specificity of word-retrieval deficits in dyslexia. Results indicate enduring problems in word-retrieval processes for dyslexic children across the primary grades and into middle childhood. Second, these deficits cannot be explained by simple vocabulary deficits. Third, these results in conjunction with our earlier data consolidate a pattern of differential relationships between specific reading and confrontation naming skills that are based on development and on the level of processes involved. Trends within case studies suggest the more pronounced the retrieval deficit, the more global the reading impairment. And fourth, there appear to be some specific differences in the basis of word-retrieval problems between dyslexic and garden-variety or lower achieving readers. Results are discussed within a speculative framework that implicates problems in timing as a possible predetermining condition in the dyslexias. o IWZ Academic PXSS, Inc. This investigation was supported in part by grants from the Biomedical Research Grant Program from Tufts University and the Educational Foundation of America. The authors are grateful to the teachers, students, and administrators of the Waltham Public School System, particularly Dr. Alan Aymes, Assistant Superintendent, for their help and cooperation in all phases of this work. We also express our gratitude to Harold Goodglass and Mary Hyde for their past conceptual and financial support of error analyses in the Boston Naming Test. Address correspondence and reprint requests to Maryanne Wolf, Eliot-Pearson Department of Child Study, Tufts University, Medford, MA 02155. 219 0093-934x/92 $3.00 Copyright 0 1992 by Academic Press, Inc. All rights of reproduction in any form reserved.

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In a review of dyslexia research, Ellis (1987) stated that “ultimately whatever dyslexia may or may not be, it cannot be a reading disorder” (p. 249). Invoked here is the view that the cognitive and linguistic processesunderlying reading are not preformed in fetal development specific to reading, but rather grow out of other cognitive capacities (for a different view, see Marshall, 1984). Ellis stressed the need in dyslexia research for attention to other cognitive systems that may utilize major processes that are then also used later in reading: for example, visual, semantic, and phonological processes. It is our contention in the research to be presented here that the word-retrieval system-with its incorporation of these and other reading-related processes-provides a unique view of the precursors and impediments to reading development. This study describes the last 2 years of the first, 5-year longitudinal examination of confrontation picture naming and reading development in the 5- to lo-year age period in average and dyslexic children. The rationale for selecting the word-retrieval process is two-part and based largely on work in the acquired aphasias and the developmental dyslexias. The first reason is based on the structural similarities in cognitive processes between naming and reading systems. Research on intact and impaired naming by aphasic patients has shown that the retrieval of words from lexical storage includes an extensive continuum of components from attention, memory, and perception through semantic, phonological, and motoric operations (see Goodglass, 1980)-all of which can be found in reading (Seymour, 1973, 1979, 1986; Wolf, 1979, 1982, 1991a). The second reason involves the demonstrated usefulness of naming tasks for probing language dysfunction. The cognitive complexity of the wordretrieval process, its sensitivity to disruption, and its relative ease in testing have made the investigation of different kinds of naming skills a critical tool for understanding brain-language relationships in the aphasias (Goodglass, 1980; Goodglass, Hyde, & Blumstein, 1969; Goodglass & Kaplan, 1972; Kohn & Goodglass, 1985). More recently, the examination of naming deficits in children has proven an important window into normal language development and language disruption, particularly in the developmental dyslexias (Gleason & Wolf, 1988; Katz, 1986; Lovett, 1987; Murphy, Pollatsek, & Well, 1988; Wolf, 1982). Some of the research indicates that the most frequently noted characteristic in children with dyslexia outside their presenting reading impairments is “subtle dysnomia” (Rudel, 1985). This appears in a variety of forms from slowed naming accessspeed on rapid automatized naming (RAN)* tasks to generative naming problems (Bowers & Swanson, in ’ Rapid automatized naming tests are serially presented or continuous naming tasks where the subject names visually presented sets (5 stimuli repeated 10 times) of highly routinized stimuli (letters, numbers, colors, objects).

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press; Denckla & Rudel, 1976a, b; Rubin & Liberman, 1983; Spring & Davis, 1988). In addition to naming deficits on experimental tasks, Murphy et al. (1988) have found significant differences in one major group of dyslexics in more natural speech contexts, specifically in story-retelling narratives. Further, there appears to be growing evidence that naming-speed deficits may be one area, in addition to phonological processing deficits (Stanovich, 1988a), that are specific to dyslexia (Bowers, Steffy, & Tate, 1988; Wolf, in press): that is, deficits present only in dyslexic readers and not found in the broad category of general or garden-variety poor readers (Gough & Tunmer, 1986; Wolf & Obregon, 1989). The latter group reads at depressed levels that are similar to those of dyslexic readers, but for other reasons, such as generally lower achievement or IQ scores (see Stanovich, in press, for discussion of IQ in dyslexia classification). Most recently, there is now evidence (Wolf, 1991b) that there are significant retrieval-speed differences between dyslexic and reading age-matched children. That is, fourth grade dyslexic children name letters and numbers more slowly than second grade average readers, thus eliminating exposure to print as an explanation. Taken together, these findings point directly to possible connections between components in the early developing naming and later developing reading systems and also to the need for further in-depth examination of the specific retrieval-deficit hypothesis. Toward these ends, the present study of confrontation naming in the 5- to lo-year age period is one part of a larger research program which systematically investigates a continuum of word-retrieval and reading abilities. The 5- to lo-year period was chosen because it is the time immediately before and after overlearned operations are laid down in reading, thus allowing more of the microstructure of various processesin reading to be accessible to examination (see Swinney, 1981). Confrontation naming was singled out for study here for several reasons. First, it represents a more complex form of word retrieval because of its incorporation of various higher level semantic processes. Second, these process requirements make confrontation naming’s relationship to reading comprehension-with the latter’s similar higher level process emphasesof particular interest. Third, the developmental history of confrontation naming deficits in the dyslexic population is only sketchily known. This is due, in part, to the persistent problem of distinguishing primary vocabulary deficits from retrieval problems with the same stimuli. Such a distinction is particularly necessary in young dyslexic populations where it is important to know for both diagnosis and remediation which language functions are impeded at which ages over development. The measure used in this investigation is the Boston Naming Test (BNT) (Kaplan, Goodglass, & Weintraub, 1983), a frequency-based, confron-

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tation naming test, frequently administered in adult and child populations. The existing Boston Naming Test, however, has no means of addressing vocabulary/retrieval differentiation. The BNT’s phonological/semantic cue system is generally used to aid retrieval after an error is produced. This procedure-particularly phonological cues-has utility with adult aphasic populations (Pease & Goodglass, 1978), but has proven relatively ineffectual in young child populations (Kindlon & Garrison, 1984; see, however, a different use of phonological cues by Rubin, Bernstein, & Katz, 1989). To address the vocabulary/retrieval differentiation problem more directly, a new version of the Boston Naming Test was designed (Wolf & Goodglass, 1986). Included in this version is a multiple-choice component (BNT M-C), consisting of the target plus three foils (visual-perceptual, phonological, and semantic) for each picture stimulus.2 After the test is completed, the component is to be administered for each word missed by the subject. If the subject is consistently able to select the correct target from the multiple-choice array, a deficit in retrieval not vocabulary is implicated.3 In the first 3 years of this longitudinal study (Wolf & Goodglass, 1986), two major findings emerged with the multiple-choice, children’s BNT. First, we demonstrated that young dyslexic readers in grade 2 appear to have retrieval, not vocabulary, problems. Second, we showed a set of relationships between particular kinds of reading and confrontation naming abilities that was based on development and a corresponding level of operations in various matched tasks. Within the first finding, the dyslexic subjects were significantly worse than average controls at retrieving words on the BNT, but better at identifying the correct targets from the multiple-choice array. There were no significant differences on a receptive vocabulary test. Thus, we con* For example, for the target “helicopter” the following foils were selected: “wasp” (visual-perceptual); “hoptacopter” (phonological); “airplane” (semantic). The construction of the experimental, multiple-choice component was based on a corpus of over 4000 young children’s naming errors on the BNT. These errors were collected from primary grade children on the first 3 years of the present longitudinal study. Errors were coded according to a psycholinguistic coding scheme designed originally by the Boston V.A. Naming Research group for adult aphasic errors (see Kohn & Goodglass, 1985) and modified slightly here for children’s errors. Approximately 70% of children’s errors were categorized as visualperceptual, phonological, and semantic error types. A computer program was created to generate the most frequently given errors in each of these three major error types for each stimulus. These three words became the foils. 3 Alternatively, if (a) the subject makes apparently random choices, both storage and vocabulary deficit should be investigated further, or (b) if the subject consistently selects one category of foils (e.g., visual-perceptual; phonological; semantic), a deficit in that particular area should be probed in more depth.

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eluded that many young, severely impaired readers know a word, but are unable to retrieve it. Unclear from these results and unsettled in the literature is the role of later development. Murphy et al. (1988) have shown naming deficits on the Boston Naming Test (traditional version) with one group of lo- to 11-year-old dyslexic readers who have very slow RAN scores. We wished to understand whether a broader range of older impaired readers would manifest persisting retrieval problems. If so, do these problems appear to lessen, increase, or remain the same over time in comparison with average readers? And, are these problems based on later developing vocabulary problems? The latter question is prompted by findings in reading theory. For example, Curtis (1987) described the interconnectedness of reading and vocabulary development: that is, better reading comprehension enhances vocabulary growth, and vocabulary knowledge increases comprehension ability in average readers. Stanovich (1986) described the converse “reciprocal causation effects” between reading deficits and vocabulary problems. Namely, the underlying reading deficit impedes the child’s vocabulary development, which, in turn, further exacerbates the original reading problem. Based on both of these conclusions, we wished to examine whether vocabulary plays a more prominent role in later word-finding deficits. In the second finding in our earlier study, we argued that in the kindergarten to grade 2 period a significant relationship exists between confrontation naming retrieval processes and reading comprehension, even when receptive vocabulary knowledge is partialled out (Wolf & Goodglass, 1986). As discussed earlier, there also appeared to be a distinct pattern of relationships between retrieval performance and reading, dependent upon the level of operations (higher or lower level) emphasized in the particular reading task. For example, the BNT had a significant but weak relationship with word recognition, which emphasizes lower level processes,and a robust, strongly predictive relationship in the primary grades with reading comprehension, which places more emphasis on higher level processes. The question remained whether this particular pattern of operation-differentiated relationships is maintained in later stages of reading development. In the present study of average and dyslexic readers in grades 3 and 4, we tested our earlier conclusions in the next stage of reading development during which time the requirements of reading have shifted from automaticity skills to a heavier emphasis on comprehension (Chall, 1983; Ehri & Wilce, 1985; Frith, 1985; Snowling, 1987). In addition, we analyzed our data in a new way to address the emerging question of whether retrieval deficits are specific to dyslexia or appear across all poor readers. Thus, we reanalyzed all 5 years of the longitudinal data with group com-

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parisons that include average and dyslexic readers and a group of gardenvariety poor readers from within the study. Specifically, four questions were addressed: (1) Do word-retrieval problems, as measured on the Boston Naming Test, persist for most dyslexic readers in grades 3 and 4? What proportion of dyslexic children manifest no or few confrontation naming problems? (2) Are word-retrieval errors in dyslexic performance based (increasingly) on underlying vocabulary problems, as ascertained by performance on the BNT multiple-choice component? (3) What is the general relationship in later grades between wordretrieval performance and particular kinds of reading, as measured by tests of word recognition, silent reading comprehension, and oral reading abilities? Are there qualitative differences in patterns between specific reading deficits and specific word-retrieval deficits among individual dyslexic readers? (4) Are word-retrieval problems in confrontation naming specific to dyslexic readers or do they appear across the class of all dyslexic and garden-variety poor readers? Finally, we attempted to place findings for these questions within a broader context of possible underlying explanations for the connections between word-retrieval and reading problems. METHODS Subjects The sample consisted of 89 children in three elementary schools in the Waltham, Massachusetts School District, chosen for its range of upper-lower through upper-middle socioeconomic status families. Children were tested for 5 consecutive years at the end of each school year from kindergarten to grade 4 on a large battery of naming and reading measures; data from grades 3 and 4 for confrontation naming and reading were the focus here (for overviews of other aspects of the study in Years 1 to 3, see Wolf, 1986; Wolf & Gow, 1986; Wolf, Bally, & Morris, 1986). The composition of the group at the end of grade 4 is described in Table 1 and broken down into three groups. In order to conduct repeated measures analyses, subjects with missing data for any of the 5 years were excluded in the present analysis. Thus the overall sample had 74 Ss: 34 females, 40 males, 67 right-handed, 7 left-handed. There were no participants in the study who possessed physical, emotional, or intellectual handicapping conditions. No child in the sample had been referred for clinical evaluation before kindergarten testing. In the present study data were analyzed only for monolingual subjects. (For a study of the BNT in a larger sample of bilingual average and impaired readers, see Novoa & Wolf, 1984; Novoa, 1988.) A central issue in the dyslexias research concerns definition and criteria for subject inclusion. Underlying this issue for many current researchers is the question of deficit specificity: that is, whether there is any deficit specific to the dyslexic child (see discussions by Ellis, 1985, 1987; Stanovich, 1988b) or whether there is simply a continuum of poor and very poor readers (see Seidenberg, Bruck, Fomarolo, & Bachman, 1985). As discussed in

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TABLE 1 SUMMARYSTATISTICS (FLUENTENGLISHSPEAKERS) Beginning sample: (15 with missing information in some year Final sample: Dyslexic readers: 2 females 0 left handed 2 right handed Garden-variety poor readers: 12 females 1 left handed 11 right handed Average-to-able readers: 20 females 3 left handed 17 right handed

N = 89 or years) N = 74 N=8 6 males 0 left handed 6 right handed N = 24 12 males 2 left handed 10 right handed N = 42 22 males 1 left handed 21 right handed

the introduction, one major approach to confronting the issue of specificity is to compare the dyslexic group with “garden-variety” poor readers (Gough & Tunmer, 1986), who are reading at similar poor levels but are not categorized as dyslexics due to such factors as depressed IQ or achievement scores. As Stanovich (1988b) stated, the inference is that if these two groups differ in cognitive subprocesses, they are arriving at reading comprehension through alternate (i.e., different) routes. To confront these and other classification issues, severely impaired readers in this study were divided into dyslexic and garden-variety groups. Eight monolingual children were classified as dyslexic readers. As seen in Table 1, a 3: 1 male/female ratio was found. There were no left-handers, as classified on a neuromotor and handedness battery administered by a neurologist and a neuropsychologist. The criteria for classification were: (1) a grade equivalent score of 2 years or more below expected scores (see Rudel, 1985; Vellutino, 1979) at the end of grade 4 on the Gray Oral Reading Test and/or the Gates-MacGinitie reading comprehension test (see discussion of cutoff scores by Fletcher, Espy, Francis, Davidson, Rourke, & Shaywitz, 1989); (2) teacher recommendation; (3) no known neurological, emotional, intellectual, or environmental factors underlying the failure (these factors were established at start of study with the cooperation of school district officials, local school principals, and classroom teachers); (4) no significant differences on IQ or IQ-related scores with average readers; and (5) consistent meeting of these criteria in grades 3 and 4. In addition, although not used as a formal criterion so as not to exclude possible subtypes, most but not all dyslexic readers performed one standard deviation or more below the mean on a nonstandardized word-recognition accuracy measure that was divided into phonologically regular, phonologically irregular, and nonsense words (see Table 3). (Note: each of these categories is broken down for dyslexic readers in the later discussion of case study analyses.) The criteria were selected to conform simultaneously to standard cutoff definitions of severe reading disability or dyslexia (see Rudel, 1985; Vellutino, 1979) and to confront two issues in longitudinal research with younger reading-impaired children: heterogeneity of

WOLF AND OBREG6N TABLE 2 GRADE EQUIVALENT MEANS AND STANDARD DEVIATIONS FOR READING TESTS BY DYSLEXIC, GARDEN-VARIETY POOR,AND AVERAGE-TO-ABLE READERS

Reading ability Dyslexic

Grade 2“ Grade 3 Grade 4

Grade 2 Grade 3 Grade 4

Garden-variety poor

Average

Means (SD) Gray Oral Reading Test 2.05 (1.367) 2.24 (0.361) 2.34 (1.658) 3.08 (0.792) 2.31 (1.352) 3.10 (0.654) N=8 N = 24

3.51 (1.440) 4.91 (2.164) 6.25 (2.574) N = 42

Gates-MacGinitie Reading Comprehension Test 1.80 (0.735) 2.70 (0.807) 2.48 (0.583) 2.97 (0.967) 2.33 (0.671) 3.72 (1.091) N=8 N = 24

4.08 (1.111) 5.26 (1.445) 6.53 (2.092) N = 42

’ All measures administered at end of school year. reading disorders and developmental change. As documented in the literature for typology of dyslexia (Doehring, Trites, Patel, & Fiedorowicz, 1981; Fisk & Rourke, 1979; Fletcher & Morris, 1986; Frith, 1985; Lovett, 1984; Mattis, French, & Rapin, 1975), no single reading cutoff measure provides sufficient information for the identification of possible reading subgroups. The use of both standardized oral reading and silent comprehension measures and also three word-recognition measures assured that major subgroups would not be ignored (for discussion of word-recognition measures in dyslexia classification, see Siegel, 1989). Also conforming to conventional criteria for severely impaired readers, 24 garden-variety poor readers were classified like dyslexic readers with the exception of the IQ-related and consistency criteria. The garden-variety poor readers were significantly different from average readers on the Peabody IQ-related measure, administered in early grades. We are aware that at least some of the garden-variety poor readers would have been classified as dyslexic readers in other research. We chose a conservative route in our classification and are confident that the actual dyslexic subjects would be categorized as such according to most other classification schema. Within these strict cutoff criteria, dyslexic readers consistently scored lower than garden-variety readers on the described oral reading, reading comprehension, and general word-recognition measures in grades 2, 3, and 4 (see Tables 2 and 3). Forty-two children were classified as average-to-able readers. Means for PPVT IQ and reading-grade equivalents for each group along with descriptive information on age, sex, and handedness are summarized in Tables 1 through 3.

MATERIALS Lexical Measures Boston Naming Test (BNT). The 1983 edition (Kaplan, Goodglass, & Weintraub, 1983) consists of 60 line drawings (by Osa Segal) of objects, presented in an order of descending word frequency. The children’s version of the BNT includes a multiple-choice component to be given after the test has been administered. The component consists of four choices for each BNT item: the target and three foils based on the most frequently given phono-

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TABLE 3 MEANS AND STANDARD DEVIATIONS FOR DYSLEXIC, GARDEN-VARIETY POOR,AND AVERAGETO-ABLE READERSON PEABODYPETIJRE VOCABULARY TEST IQ-RELATED SCORESAND ON Worm RECOGNITION SCORES

Reading ability Dyslexic

Kindergarten Grade 2

Grade 3 Grade 4

Garden-variety poor

Average

Means (SD) Peabody Picture Vocabulary Test 105.0 (12.036) 98.5 (15.557) 104.9 (12.029) 101.1 (12.803) N=8 N = 25

113.0 (14.364) 109.5 (8.631) N = 42

Total Word-Recognition” Measure 10.0 (6.68) 14.25 (3.13) 14.0 (5.88) 17.75 (3.0) N=7 N = 24

17.8 (3.2) 20.57 (2.52) N = 40

a Includes eight phonologically regular, eight phonologically irregular, and eight nonsense words; this score not used as criterion for reading impairment to preserve possible subtypes.

logical-, semantic-, and perceptual-based errors of children from 5 to 7 years. (A revised version based on an error corpus by children from 5 to 10 years is now available.) The corpus of children’s errors was analyzed according to a linguistic coding scheme originally designed by the Naming Research Group at the Boston Veteran’s Administration Hospital Aphasia Research Center4 (See Kohn & Goodglass, 1985).

Reading Measures Gates-MacGinitie Rending Comprehension Test (Gates & MacGinitie, 1978). The test measures silent reading comprehension, consists of short paragraph passages with one multiple-choice question following each passage, and is standardized with grade-equivalent norms. Gray Oral Reading Test (Gray, 1967, Form A). This test measures oral reading ability. The student reads aloud as many graded and timed reading passages as possible. Errors are categorized and the test is standardized with grade-equivalent norms. Word-recognition tasks. This measure consists of three individual lists of words presented on charts made of l/4-in. white 327-C Formecor board. The three word categories chosen were (1) nonsense words; (2) phonologically regular words; and (3) phonologically irregular words. These categories were chosen in order to assessboth direct lexical-access procedures (phonologically irregular “sight words”) and nonlexical, phonological-access procedures (nonsense and regular words). Eight monosyllable high-frequency words were chosen for each list. The nonsense list was composed of eight phonologically regular, monosyllabic nonsense words, selected from third and fourth grade phonic workbooks. The phonologically regular and phonologically irregular words were chosen from third and fourth grade texts.

4 The authors thank members and former members of the Boston V.A. Hospital Aphasia Research Center Naming Group directed by Harold Goodglass, particularly Jean Berko Gleason, the late Carol Biber, Eugene Green, Mary Hyde, Susan Kohn, Jacqueline Liederman, Lise Menn, and Art Wingfield.

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MEANS AND STANDARDDEVIATIONS FORDYSLEXIC, GARDEN-VARIETY POORREADERSON THE BOSTON NAMING TEST AND BNT MULTIPLE-CHOICE ITEMS IN GRADES 3 AND 4

Reading ability Dyslexic

Grade 3 Grade 4 Grade 3 Grade 4

33.3 (6.0) 34.9 (4.4)

Garden-variety poor Means (SD) Boston Naming Test 31.2 (12.5) 37.0 (5.8)

Boston Naming Test Multiple-Choice 7.6 (2.1) 6.3 (2.0) 7.4 (2.1) 6.3 (1.7)

Average

38.5 (5.7) 42.4 (5.6) 5.4 (1.9) 5.5 (1.9)

Procedure Lexical Measure Boston Naming Test procedures require an oral response to line drawings. The child is shown a drawing in a spiral-bound test booklet and asked to name the picture as accurately and quickly as possible. If the child fails to name an item correctly or at all, latency is not recorded and the subject is encouraged to try again until a total of 15 set have elapsed. All attempts and error responses are recorded on the instructor’s sheet for later coding. All uncorrected, missed items are checked on the multiple-choice list, kept by the experimenter. After the child has completed all items or, as in the Peabody Picture Vocabulary Test (Dunne & Dunne, 1981), misses six of eight consecutive items, the multiple-choice component is administered. The experimenter reopens the test booklet to each of the missed items and reads a list of four words (one target, three foils) two times for each missed stimulus. The child must choose one of the four items. All responses are recorded. At the end of grades 3 and 4, reading measures were administered in both individual and group sessions. Standardized instructions were used for the Gray Oral Reading and GatesMacGinitie Silent Comprehension Test. In the oral reading format children read graded passagesfrom a small spiral-bound booklet in individual sessions.The experimenter recorded all errors and latency on standardized forms. In the silent reading-comprehension test, administered in a separate group session, children read as many graded passagesas they could within a fixed time limit. Written comprehension questions followed each passage. Scores for both tests are based on accuracy and time. In the word-recognition task, each child was asked to read each word list chart as accurately and as quickly as possible. To make both total and individual category latencies available for analysis, latency was recorded with a Micronta 65-5009 digital stopwatch, which records to the 100th msec for the time from the first to the last item on each chart. Errors and self-corrections were recorded and included in latency as process-indicative (see Rude& 1985). When a child made an error, he or she was encouraged to try again and continue. In instances of visible frustration or attempts longer than 15 set, the child was given the correct word and told to continue or begin the list again if desired. In such cases, the latency data were eliminated and only the accuracy score for first attempts at an item was recorded. On the nonsense word list, pronunciation of a word was counted correct as long as it preserved the consonant structure and one possible pronunciation of the target vowel(s).

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RESULTS Summarized in Table 4 are the means for the BNT and BNT M-C scores of average, garden-variety, and dyslexic readers. Note that means for average readers (Grade 3 X = 38.5; Grade 4 X = 42.4) closely approximate BNT means collected by Guilford and Nawojczyk (1988) (Grade 3 X = 38.3; Grade 4 X = 41.1). Question 1: Group Differentiation: Dyslexic vs. Average Readers The first question was the persistence of retrieval problems among dyslexic readers in grades 3 and 4 as a group and as individuals.’ The ability of confrontation naming performance to differentiate Reading Group was assessedby a mixed design 2 (Reading Group) x 2 (Year) MANOVA with repeated measures for Year. Results indicated significant main effects for Reading Group (F(48, 1) = 9.82; p < .Ol) and Year (F(48, 1) = 15.32; p < .OOOl). There were no significant interaction effects. Results were broken down for each year and indicated significant differences favoring average readers on the BNT in grade 3 (F(48, 1) = 5.6, p < .02) and grade 4 (F(48, 1) = 12.7; p < .OOl). Note that individual performances on the BNT and BNT M-C scores by each dyslexic subject will be presented under Case analyses for question 3. Question 2: Retrieval/Vocabulary Distinctions The second question, whether readers’ naming deficits are the result of blatant vocabulary-knowledge deficiencies, was assessedby the BNT multiple-choice score and was analyzed by a mixed design 2 (Reading Group) x 2 (Year) MANOVA with repeated measures for Year. Results indicated significant main effects for Reading Group in grade 3 (F(47, 1) = 10.22; p < .Ol) and grade 4 (F(47, 1) = 6.05; p < .Ol). Note from the means that this analysis favors dyslexics. That is, after a word-finding error occurred, many dyslexic readers were more likely than average readers to identify the correct target in a multiple-choice array. To control for the possibility that the multiple-choice results favoring dyslexic readers were simply an artifact of more actual attempts, a third 2 x 2 MANOVA with repeated measures for Year was conducted for total multiple-choice items attempted. There were no significant main effects for Reading Group (F(1, 70) = 2.7) or Year (F(2, 140) = .06). (Note: the total BNT score is based not only on errors, but also on highest item achieved.) Thus, this pattern results in: (a) a diminished opportunity ’ In a separate study of gender differences in word retrieval from kindergarten to grade 3, there were significant gender differences (p < .05) favoring males (see Wolf & Gow, 1986).

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to continue to the final deciles of the test; (b) a lower score; but (c) a similar number of errors with average readers. These results suggest that no explanation of BNT naming deficits based largely on vocabulary knowledge is appropriate at any year of our testing. In particular, the consistent performance of most impaired readers on the multiple-choice format points toward the hypothesis that for impaired readers the target word is stored at some level along a continuum of word knowledge (see Beck, Perfetti, & McKeown, 1982), but is not available for normal word retrieval. (It is important to emphasize here that this pattern may be altered in different socioeconomic and educational environments where vocabulary knowledge might be significantly different and this retrieval/vocabulary distinction rendered irrelevant.) Question 3: Retrieval-Reading Relationships The relationships between confrontation naming ability and different reading operations were assessedin two ways: quantitatively across groups by Spearman listwise correlations, presented in Tables 5, 6, 7, and qualitatively among dyslexic readers by case analyses presented in Tables 8, 9, and 10. Correlation matrices are reported first for the entire monolingual population and second for the sample’s average readers to show the reading-retrieval relationships when impaired reading subjects are removed. Results indicate significant relationships between BNT (in grades 3 and 4) and each reading variable. Similar to previous results, the pattern of the relationships appears to be the following for both populations: strong relationships between the BNT and the two higher level reading operations (i.e., reading comprehension and oral reading) and significant, but relatively weaker relationships with word recognition. To further assessthe developmental prediction capacity of the BNT and the three reading measures, data from the first 3 years of the longitudinal study were merged with the present data set for Years 4 and 5. As reported in Table 7, results from Spearman correlations for the entire TABLE 5 SPEARMAN CORRELATIONS FOR THE ENTIRE (BNT) AND THREE READING

Word recognition

Grade 3 BNT Grade 4 BNT ** p < .Ol. *** p < .ool.

POPULATION BETWEEN BOSTON NAMING VARIABLES IN GRADES 3 AND 4

Oral reading

TEST

Reading comprehension

Grade 3

Grade 4

Grade 3

Grade 4

Grade 3

Grade 4

.37**

.22 .34**

.43**

.49*** SO**’

.58***

.61*** .49***

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TABLE 6 SPEARMAN CORRELATIONS FORTHE AVERAGEREADERPOPULATIONBETWEENBOSTONNAMING TEST (BNT) AND THREEREADINGVARIABLESIN GRADES3 AND 4 Word recognition

Grade 3 BNT Grade 4 BNT

Oral reading

Reading comprehension

Grade 3

Grade 4

Grade 3

Grade 4

Grade 3

Grade 4

.36***

.29** .42***

.26**

.39*** .48***

.45***

.51*** .51***

** p < .Ol.

*** p < ml.

population indicate that kindergarten, grade 1, and grade 2 BNT performances are consistent, strong predictors of grade 4 reading comprehension and oral reading, and significant, but only modest predictors of word recognition. The same pattern is maintained in correlations for the average reader population. Case Analyses

Table 8 presents data on individual performances on the BNT and BNT M-C by each dyslexic subject, alongside average reader means. Note that in grade 3 and 4, two dyslexic readers consistently evidenced BNT scores similar to those of average readers. Thus, in this small sample of very severely impaired readers where socioeconomic and educational environments are controlled, one-fourth of the dyslexic subjects did not have depressed scores on the BNT. (Note: in settings where socioeconomic conditions strongly, negatively influence the educational environment, we would expect more negative findings on all vocabulary-related indices.) Among dyslexic children there was one typical global-impairment pattern between specific reading deficits and word-retrieval performance and three distinct mixed-deficit patterns. The presence of such diversity in this TABLE I SPEARMANCORRELATIONS” FORTHE ENTIRE POPULATIONBETWEENBOSTONNAMING TEST (BNT) IN KINDERGARTEN, GRADE1, GRADE2, AND THREEREADINGVARIABLESIN GRADE4

Kindergarten BNT Grade 1 BNT Grade 2 BNT

Word recognition

Oral reading

Reading comprehension

.35 .31 .32

.55 .47 .46

.59 .60 .55

y All correlations significant at p < ,001.

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WOLF AND OBREG6N TABLE 8

INDIVIDUAL

SCORES ON

THE BOSTON NAMING TEST (BNT) AND THE BOSTON NAMING MULTIPLE-CHOICE (BNT M-C) BY 8 DYSLEXIC SUBJECTS

TEST

Total correct Grade 3 Dyslexic subject

BNT

BNT M-C

BNT

BNT M-C

25 27 28 33 36 37 39 41

6 10 11 8 6 7 8 5

31 27 36 36 35 34 41 39

5 9 7 5 No data 11 8 7

34.9 (4.4) 42.4 (5.6)

(2.1)

33.25

Dyslexic

(6.0)

38.5 (5.7)

Average

Grade 4

Group means (SD) 7.6

(2.1)

5.35 (1.9)

7.4

(G)

small sample is indicative of the complexity of both systems and the extent of heterogeneity present among dyslexic readers. Pattern 1: Global reading-naming impairment. Deficits across all reading variables with lowered BNT and higher BNT M-C scores. (Subjects 2, 3, 6; Subjects 1 and 5, except for BNT M-C.) The first pattern of global deficits across all reading and naming variables is clearly the most typical pattern for this group of dyslexic children and possibly for the majority TABLE 9 INDIVIDUAL

GRADE-EQUIVALENT

SCORES ON THE STANDARDIZED EIGHT DYSLEXIC SUBJECTS

TESTS FOR THE

Gates

Gray Subject

READING

Grade 3

Grade 4

Grade 1

Grade 2

Grade 3

Grade 4

2.0 1.5 1.6 6.4 1.9 1.4 2.0 1.9

2.0 1.6 1.6 5.6 2.2 2.5 2.0 2.0

1.6 1.3 1.4 2.0 1.4 1.5 1.6 1.7

1.6 1.4 1.7 3.6 1.4 1.6 1.5 1.6

1.5 2.9 2.2 3.4 2.3 1.9 2.5 2.5

2.9 1.4 2.4 3.5 1.6 2.1 2.4 2.3

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NAMING AND DYSLEXIA TABLE 10 INDIVIDUAL

SCORES ON THE WORD-RECOGNITION MEASURES’ DYSLEXIC SUBJECTS

FOR THE EIGHT

Total correct

Subject

Grade 3

Grade 4

Nonsense

Irregular

Regular

Grade 3

Grade 4

I 0 3 8 3 1 8 4

5 1 4 4 1 1 6 2

Grade 3

Grade 4

a Each list has a total of eight words.

of other impaired reading populations. These subjects had the lowest reading scores across all three types of reading, the lowest BNT scores, and the highest BNT M-C scores. Thus, the global-impaired subgroup exhibited the strongest and most unambiguous retrieval deficits among the dyslexic subjects. The following three patterns are of particular interest because they do not follow typical dyslexia characteristics, particularly in their dissociation between preserved phonological skills in word recognition for regular and nonsense words and their impaired comprehension. In addition, two of these subjects had BNT scores within the average range and ambiguous scores on the BNT M-C. Pattern 2: Dissociated word recognition and comprehension. Preserved word recognition and superb oral reading; impaired comprehension and impaired naming with average BNT M-C (Subject 4). Case 4 exhibited a highly unusual dissociation in children’s reading between a severe comprehension deficit and spared performance on all other reading skills. This reader achieved uniformly near-perfect scores in word recognition and achieved grade equivalents 2 to 3 years above his grade level in oral reading. His reading-comprehension grade equivalent scores of 3.6, 3.4, 3.5 (in grades 2, 3, and 4) reflect his excellent decoding and the emphasis on decoding in early reading. Yet, these scores plateau at the third grade level because reading-comprehension requirements become increasingly sophisticated around grades 3 and 4 and go well beyond word-recognition requirements. Thus, this subject only appeared reading-impaired in higher elementary grades. His word-retrieval performance was generally poor; and unlike

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other dyslexic readers, his BNT M-C was similarly depressed, thus making a retrieval deficit per se ambiguous. Pattern 3: Impaired oral reading and comprehension with preserved word recognition and naming. Average BNT, but with higher BNT M-C. Subject 7 had preserved word recognition across regular, irregular, and nonsense words, but both impaired oral reading and comprehension. Despite his apparently preserved BNT scores, this subject’s very high BNT M-C score indicates a potential, otherwise undetected, retrieval problem. Pattern 4: Mixed word recognition. Preserved phonologically regular and nonsense words; impaired irregular words; impaired oral reading and comprehension; average BNT and BNT M-C (Subject 8). Subject 8 exhibited perhaps the most unusual profile: average-to-good word recognition scores for phonologically regular and nonsense words, but very poor word recognition for phonologically irregular sight words like “pint” or “yacht.” Because of this dissociation, original latency data were also examined. Latencies exhibited the same pattern and were twice as long for irregular words as for regular words. Comprehension and oral reading were very impaired, but word retrieval was within the norm. This profile appears to resemble most closely that disorder group which falls under the category of surface dyslexia: that is, reading failure based on deficits (often fluctuating) at the word level, with preserved phonological “subword” (Patterson, Marshall, & Coltheart, 1985) level knowledge. Taken together, the findings for these mixed-deficit subjects are highly suggestive of the enormous diversity of dissociations between systems that may influence and/or underlie reading disruption. Question 4: Deficit Specificity: Dyslexic versus Garden-Variety Poor Readers To examine the specific nature of confrontation-based retrieval deficits among dyslexic readers, a series of mixed design 3 (Reading Group) x 2 (Year) MANOVAs with repeated measures for Year were conducted for garden-variety poor readers, average readers, and dyslexic readers. These MANOVAs were performed for the BNT scores and for the BNT M-C scores in grades 3 and 4. Results for the BNT indicated significant group differences (F’(11, 2) = 10.68; p < .OOOl). A breakdown by group and year indicated significant differences in grade 3 (F(66, 1) = 9.13; p < .Ol) and in grade 4 (F(66, 1) = 17.7; p < .OOl) on the BNT between garden-variety and average readers, but no significant differences between garden-variety and dyslexic readers. Overall results for the BNT M-C showed significant group differences (F(70, 2) = 8.42; p < .OOOl). A breakdown indicated significant differences between dyslexic and average readers on the BNT M-C (as reported in Question 2)) but no significant group differences between garden-variety

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and average readers. There were no significant differences between dyslexic and garden-variety readers on BNT M-C, although results approached significance (p < .lO). Together, results on group differentiation between garden-variety and dyslexic readers for the BNT and BNT M-C indicate no differences in the actual performance on the BNT, but significant differences for the reasons underlying the depressed scores on the BNT M-C. Many dyslexic readers appear to know the word, but cannot retrieve it. Garden-variety readers appear more similar to average readers on the BNT M-C: that is, both of the latter groups more frequently miss a word because they do not know it, rather than because they cannot retrieve it. DISCUSSION The present research represents the final 2 years of a 5-year longitudinal investigation of (a) confrontation-based word-retrieval deficits in dyslexic children; (b) the role of vocabulary development in these deficits; (c) the relationship between confrontation naming performance and three aspects of reading both in the general population and in case analyses of dyslexic subjects; and (d) the possible specificity of word-retrieval deficits in dyslexia. Results indicate enduring problems in word-retrieval processes for most dyslexic children across primary grades and into middle childhood. Second, these deficits cannot be explained by simple vocabulary deficits. Third, these results when combined with our earlier data consolidate an overall pattern of differential relationships between specific reading and confrontation naming skills. These relations are based on development and on the type of cognitive processes involved. There is diversity in patterns between reading and naming skills among individual dyslexic subjects hypothesized to be connected to the nature of the reading deficits. Fourth, some specific differences in the baszkof word-retrieval problems are found between most dyslexic readers and garden-variety or lower achieving readers. Individual Differences and Development There is a consistent, marked discrepancy between average and dyslexic readers’ word-finding ability from kindergarten through grade 4. These differences appear more pronounced over time. We conclude that many dyslexic readers possessa significant form of “subtle dysnomia” (Denckla & Rudel, 1976a) for confrontation naming during the early and middle stages of reading development. Furthermore, results on RAN retrieval tasks for highly routinized letters and digits (Bowers et al., 1988; Denckla & Rudel, 1976a, b; Hutchens, personal communication, 1987; Spring & Davis, 1988; Swanson, 1989; Wolf, 1986; Wolf, et al., 1986; Wolff, Michel, & Ovrut, 199Oa,b) indicate that naming-access speed problems persist

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well into adolescence and adulthood for large subgroups of dyslexic populations. As Ellis urged (1985, 1987), however, it is necessary to note the heterogeneity of dyslexic performance on all studied variables: two dyslexic subjects evidenced no pronounced difficulty in confrontation naming and several showed no or inconsistent advantages on the multiple-choice component, a finding that will be returned to in a later section. Vocabulary-Deficit Explanations To tease apart vocabulary knowledge from retrieval abilities, performances on the BNT M-C component were analyzed and showed no significant group differences. Further, many impaired readers were more likely than average readers in grades 2 to 4 to select the correct target in a multiple-choice array after an error was originally made. To ensure that these results were not simply an artifact of dyslexic readers making more errors, we conducted an analysis of multiple-choice attempts and found no significant differences. As word-frequency level on the BNT decreases, average readers break down because they do not know a word. This gives average readers a higher overall score, but a number of errors similar to that of dyslexic subjects. The latter break down earlier because they fail to name known words that they cannot retrieve. These results, particularly when integrated with data that indicate both prereading and enduring deficits on the more basic retrieval tests, reinforce our conclusion that confrontation naming deficits in dyslexic readers cannot be explained by simple reference to vocabulary. Such a conclusion, however, cannot be generalized across different socioeconomic environments and does not mean that vocabulary plays no role, particularly in older dyslexic readers. As discussed earlier, Chall (1983), Curtis (1987), Perfetti (1985), and Stanovich (1986) have demonstrated the interconnectedness of reading and vocabulary development and the “reciprocal causation relationship” (Stanovich, 1986) between reading deficits and later vocabulary problems. The increasingly pronounced deficits in performance on the BNT were not expected and may well have been influenced by a concomitant stunting of vocabulary development and/or failure to establish more elaborated semantic networks (see Kail & Leonard, 1986; McGregor & Leonard, 1989), not measured by our tasks. [Note: In an ongoing study, we analyze retrieval and vocabulary in dyslexic children across a variety of tasks and contexts so as to examine the nature and level of stored knowledge for unretrieved words and the more subtle influences of vocabulary knowledge on retrieval (Segal & Wolf, in press).] Differential Naming-Reading Relationships Our third question addresses the differential relationships between confrontation naming and three types of reading, each with different process-

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AND

DYSLEXIA

237

level emphases. Results replicate and extend the developmental, processbased, differential patterns found in Years 1 to 3: (1) strong relationships between confrontation naming and reading comprehension with both of their emphases on higher level processes; (2) modest relationships with word recognition with the latter’s lower level process emphases; and (3) relationships with oral reading (where both higher and lower level processesare used) falling generally in between. The exact converse set of relationships is found between more basic levels of retrieval (RAN tasks) and these same forms of reading: (1) strong, enduring relationships with word recognition; and (2) increasingly weak but significant relationships over time with reading comprehension (Spring & Davis, 1988; Wolf et al., 1986). By partialling out word recognition, Spring and Davis (1988) found that the relationship between comprehension and RAN tasks was explained by the shared variance with word recognition. Within a developmental context, we interpret these combined findings to mean that in the preliteracy period, most kinds of naming tasks robustly predict most kinds of later reading, a long documented predictive relationship (Jansky & de Hirsch, 1972; Johnson & Myklebust, 1964). Indeed, Scarborough has shown the ability of naming tasks in 3-year-old children to predict later reading (Scarborough, 1989). Perfetti, Finger, and Hogaboam (1978), however, found no relationship between grade 3 reading comprehension and naming-access speed for simple objects, colors, and numbers (see Discussion in Wolf et al., 1986; Wolf, 1991a).6 Between these disparate findings, we suggest, comes a complex, operation-differentiated, developmental set of changes. By the end of grade 2-that is, when lower-level processes approach automatic levels and reading acquisition is fairly complete--only specific relationships between process level-matched forms of naming and reading remain robust. Basic, simple forms of naming like rapid automatized naming tests are chiefly related to word recognition; more lexically complex forms of naming like the BNT are more strongly related to reading comprehension. Thus, subprocesseswithin the two systems have grown increasingly autonomous, and their areas of intersection increasingly discrete. Case Study Findings To understand these relationships with more specificity when pathology is involved, case analyses of each dyslexic subject were conducted. Analyses revealed one global naming-reading impairment pattern for most of the subjects and three mixed-deficit patterns. The global-deficit subgroup exhibited the strongest most unambiguous retrieval deficits and the lowest 6 Note that Perfetti et al. (1978) used a discrete-trial format to measure naming-access speed. For a discussion of these procedural differences, see Wolf (1991a), and Swanson (1989).

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reading scores across all forms. In contrast, the mixed-deficit cases manifested various patterns of preserved word recognition, severe readingcomprehension deficit, and less pronounced, possibly more subtle, retrieval deficits. These mixed-deficit profiles are infrequently seen or described. First, these students usually manifest only in later grades; second, their average to superior word-recognition skills often exclude them from typical dyslexia classification. (Note: Rude1 (personal correspondence, November, 1983) earlier emphasized the need to study this group of children with no decoding problems but significant comprehension difficulties.] The most intriguing case resembled reported cases of developmental surface dyslexia. According to Temple, surface dyslexic patients “appear to result from an overreliance on a phonological reading route, but they differ [from each other] in that the phonological reading route itself is disrupted in different ways.” (1985, p. 1). The typical patient exhibits regularity effects in reading much like our subject. Temple (1985) has described several cases of hypothesized developmental surface dyslexia, but has not included sufficient information concerning naming abilities for a comparison here. Margolin, Marcel, and Carlson (1985) have discussed a possible connection between dysnomia and adult surface dyslexia, whereby a common deficit in the phonology output lexicon disrupts both object naming and reading. For example, Margolin et al. (1985) reported one patient who exhibited similar circumlocutory errors for the same object in confrontation naming and word-recognition tasks. In reading aloud, patients with these phonology-output problems might use intact grapheme-phoneme rules to read words in a regularized fashion. But, words that require a direct, lexical route could not be processed correctly. Our subject exhibited reading deficits similar to those of some child and adult surface dyslexias described in the literature, but showed relatively preserved naming in BNT and BNT M-C. The question remains whether the latter performance reflects his actual level of vocabulary knowledge, which averaged 3 years above his grade and age level. This possible dissociation between the subject’s average BNT scores and his vocabulary level may again be indicative of a more subtle retrieval deficit. It will be important in future cases of developmental surface dyslexia to explore the role of retrieval deficits in subjects’ performances. Taken together, our case analyses revealed heterogeneity in both retrieval disruption and reading breakdown, thus giving no simple algorithm connecting specific reading and naming deficits. We cautiously suggest two tendencies in these case analyses: (1) the more pronounced the retrieval deficit, the more global the reading impairment; (2) conversely, the less pronounced and/or more subtle the retrieval deficit in dyslexic readers, the more dissociated the reading performance between word recognition and comprehension. Thus, among the mixed-deficit dyslexic readers, retrieval difficulties may be (a) nonexistent in some readers, or

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(b) requiring more refined analyses to be uncovered and understood properly. Differences in retrieval performance between reading types may well be the product of different sources of reading and naming breakdown. For example, phonological factors may explain reading and retrieval failure in the global-deficit group, but appear less likely as an explanation in the three dissociated pattern groups. Recently, Perfetti (in press) and others have discussed problems at the level of representation as a source of reading disorder. It would be of particular interest in future work to examine the dissociated reading subjects both at the level of representation abilities and also in terms of a possible deficit in the phonology-output lexicon, as hypothesized in surface dyslexia. Another possibility will be proposed in the next section. The Possible Specificity of Retrieval Deficits Our fourth and last question is, perhaps, the most unresolved and thought-provoking: that is, the possible specificity of retrieval deficits among dyslexic readers. To pursue this question, new analyses were conducted that included comparisons with garden-variety poor readers. There were no significant differences between dyslexic and garden-variety readers on the BNT or BNT M-C (although the latter approached significance). There were no differences between average and garden-variety readers on the multiple-choice component. Dyslexic readers, however, were significantly more likely than average readers to choose the correct target on the BNT M-C. Underlying the two similarly depressed confrontation naming scores by dyslexic and garden-variety poor readers appear different reasons for their poor performance. Garden-variety poor readers, like average readers, do not name a word in most instances because they do not know it; dyslexic readers more frequently know the word at some level (see discussions of semantic elaboration in Kail & Leonard, 1986; McGregor & Leonard, 1989 and discussions of levels of word knowledge by Beck et al., 1982; Kameenui et al., 1987), but cannot retrieve it. There appears, therefore, modest evidence pointing toward specific-retrieval deficits in dyslexic children. Toward an Underlying Explanation of Reading and Naming Deficits Whether the underlying source of the retrieval deficits is based on phonological problems (Katz, 1986), less fully stored semantic information (Kail & Leonard, 1986), or simply a more general oral language deficit (Murphy et al., 1988) cannot be determined by the present data. Given our generally (but not universally) shared assumption of heterogeneity in the population (Ellis, 1985), it is prudent to assume that any of these explanations may operate within a given individual or subgroup. It is our

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view that like the reading process, the very complexity of the wordretrieval process mitigates against any one unifying explanation for its breakdown. This is particularly true in developmental populations where there may be dysynchronous development across critical subprocesses. Despite the probable multifactorial basis for the many kinds of wordretrieval deficits noted among individual dyslexic children, there may be certain predetermining conditions (beyond phonological explanations) that predispose the dyslexic toward both naming problems and reading problems. Based on cumulative research on a considerable number of cognitive, linguistic, perceptual, and motor subprocesses involved in both naming and reading, we hypothesize that a strong candidate for such a predetermining condition is whatever underlies dyslexic readers’ pronounced deficits in tasks demanding rapid rates of processing. Support for this hypothesis is found in the growing body of research which indicates that most dyslexic children are significantly slower, not only at a variety of basic-level, verbal, information-processing tasks (Bowers et al., 1988; Denckla & Rudel, 1976a, b; Lovett 1984, 1987; Spring & Capps, 1974), but also at nonverbal, motoric, rate-requiring tasks (Nicolson & Fawcett, 1990; Wolff et al., 1990a). Recently, we have found that a deficit in the rate of naming appears more specific to dyslexic children than previously known. Wolf and Obregon (1989) found robust significant differences between dyslexic and garden-variety readers from kindergarten to grade 4 across all naming-access speed measures (RAN and the more complex, Rapid Alternating Stimulus or RAS measures, Wolf, 1986). Most recently, Wolf (1991b) reported significant differences between dyslexic readers and their 2-year younger, reading age-matched, average-reading counterparts. Thus, no explanation based on either general poor reading or exposure to print can be used to interpret dyslexics’ slower performance. Significant differences on nonverbal tasks raise the question of a domaingeneral rate deficit. Nicolson and Fawcett (1990) found significant differences in severely impaired readers on motor tasks that demand automaticity. They hypothesized that reading deficits may be “symptoms of a more general learning deficit, the failure to fully automatize skills” (p. 159). Wolff et al. (1990a) demonstrated persistent temporal-based difficulties in adolescent dyslexic readers on verbal RAN tasks and on a series of nonverbal, neuromotoric tasks like finger tapping. Wolff et al. (1990a) suggested that the combination of temporal requirements plus serial order differentiated their dyslexic readers (regardless of task content). Using a series of filmed tasks that require (verbal) stimulus naming (objects and colors) at different rates of presentation and different exposure times, Wolff, Michel, and Ovrut (1990b) attempted to tease apart: (a) rate; (b) timing precision; and (c) serial order. Both discrete and continuous trials distinguished reading groups. That is, temporal require-

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ments at the basic level of naming, with and without serial order, elicited significant differences. From a different paradigm, recent work by Bowers and Swanson (1991) and Swanson (1989) also demonstrated rate deficits in dyslexic readers at the most basic, discrete level of presentation of verbal symbols. A Speculative Proposal At our most speculative, we would propose that connecting these findings on naming speed and reading failure is a common timing mechanism underlying both particular language and particular motor functions (Wolf, 1991a). Ojemann (1984) described several lines of evidence supporting this form of common mechanism for some language and motor functions. For example, Ojemann (1975, 1983; Ojemann & Mateer, 1979) showed that blocking by electrical stimulation in specified anterior frontal areas caused disturbance in both sequential motor movements and speechsound identification. He suggested that a precise timing mechanism held in common between these functions might be key for both production and decoding processes. Tzeng and Wang (1984) also argued for a common timing mechanism underlying “intellectual and signal production systems” (p. 910) and regarded dyslexic readers as a potentially special case of deficits in temporal resolution. They hypothesized that severely impaired readers are unable to utilize the left hemisphere timing mechanism to code the correct letter sequence in written language and to employ grapheme/phoneme correspondence rules rapidly enough to achieve reading fluency. We wish to begin a serious consideration of this study and related findings within the context of early impediments to a timing mechanism. First, early impediments in timing for basic lower level, cognitive and linguistic processes could directly effect the development of the rapid processing and smooth integration necessary in general word-retrieval and decoding and indirectly prevent higher level processes like reading comprehension from functioning properly. [A possible variation of timing deficits might be temporal sequencing problems (see work by Bakker, 1971; Rude1 & Teuber, 1971) which would be similarly disruptive.] Second, to the extent that various subprocesses make more demands upon rapidity, these subprocesseswould be impaired accordingly. Thus, findings by Wolf et al. (1986) suggesting more pronounced speed problems for dyslexic readers for automatized (digits, letters) rather than nonautomatized stimuli (colors, objects) are explained according to more extensive use of timing properties by automatized stimuli. The present findings indicating differential problems in confrontation naming for dyslexic and poor readers could be explained by speed-influenced retrieval problems for dyslexic readers and vocabulary-related problems for garden-variety poor readers.

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It is critical to reiterate our position that the dyslexias represent a heterogeneous group of impaired readers. We offer no new unifying explanation, but rather a possible factor that could underlie or add to other hypothetical “specific deficits” like phonology, and thus disrupt the entire reading system. Integrating such a conceptualization with conventional explanations for the developmental dyslexias, we suggest several minimal conditions, each of which could result in reading failure: (1) a general propensity toward slower functioning based on the failure of a specific timing mechanism; (2) a combination of timing mechanism failure plus failure in major cognitive subsystems like phonology, memory (see Shankweiler & Crain, 1986), or representation (see Perfetti, in press); or (3) as is currently emphasized, specific, major subsystem failure. Each of these conditions, we hypothesize, can result in severe reading failure. Such a conceptualization, however, raises more questions than it answers.7 For example, Doehring (personal correspondence, May 1, 1991) suggested several critical areas for any discussion of timing: (1) the domain-specific or domain-general nature of any timing mechanism; (2) separation between timing for perception and timing for production; and (3) accounting for such issues as minimum duration, rhythm, seriation, sequence recall vs. pattern recognition, single vs. repeated stimuli (identical vs. different), etc. A preliminary treatment of some of these issues is found elsewhere (Wolf, 1991a), but clearly many essential research questions remain open about the nature of such a mechanism(s) and how it might develop over time. Our purpose in this speculative proposal is to raise these issues to the status of explicit questions in the developmental dyslexias. SUMMARY This 5-year, longitudinal investigation of the confrontation naming process demonstrated: the enduring and heterogeneous nature of word-retrieval deficits in the developmental dyslexias population; the relatively minor role of gross-level vocabulary knowledge in these deficits in early and middle childhood; and the increasingly differentiated, process levelbased pattern of relationships between confrontation naming and three aspects of reading. Case study analyses can be cautiously interpreted as ’ Another question emerges from data by Tallal, Stark, and Mellits (1985), who hypothesized similar temporal resolution problems as the basis for language-disordered children’s deficits, as separate from a group of dyslexic children. In addition to our arguments against a single-deficit hypothesis, a critical issue here is that Tallal et al. (1985) carefully screened dyslexic subjects to exclude all language impairments. Most typologies indicate that the largest subgroups of dyslexic children have some form of language problems. The question emerges, therefore, whether subgroups of dyslexic children with language impairments (unstudied by Tallal et al., 1985) evidence underlying temporal resolution problems.

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a tendency toward more pronounced naming problems in more globally, severely impaired readers and more ambiguous naming deficits in dyslexic readers with mixed-reading deficits. These results in conjunction with other research also provided tentative support for a different, highly speculative, specific-deficit hypothesis among many dyslexic readers; namely, a deficit in timing. More questions were raised than answered in this fourth area, and the need for further research is clearly indicated. The original question of our research program is more resolved and directly addresses Ellis’ injunction to find early developing cognitive systems that share processes with later developing reading systems. This study suggests that the developing word-retrieval or naming system offers both a developmentally early analogue to the later acquired reading system and a powerful tool in the prediction and study of specific subprocesses in reading pathology. REFERENCES Bakker, D. J. 1971. Temporal order in disturbed reading: Developmental and neuropsychological aspects in normal and reading retarded children. Rotterdam: Rotterdam Univ. Press. Beck, I. L., Perfetti, C. A., & McKeown, M. G. 1982. Effects of long-term vocabulary instruction on lexical access and reading comprehension. Journal of Educational Psychology, 74, 506-521. Bowers, P. G., Steffy, R., & Tate, E. 1988. Comparison of the effects of IQ control methods on memory and naming speed predictors of reading disability. Reading Research Quarterly, 23, 304-319.

Bowers, P. G., & Swanson, L. B. 1991. Naming speed deficits in reading disability: Multiple measures of a singular process. Journal of Experimental Child Psychology, 51, 195 219. Chall, J. S. 1983. Stages of reading development. New York: McGraw-Hill. Curtis, M. E. 1987. Vocabulary testing and vocabulary instruction. In M. G. McKeown & M. E. Curtis (Eds.), The nature of vocabulary acquisition. Hillsdale, NJ: Erlbaum. Pp. 37-51. Denckla, M. B., & Rudel, R. G. 1976a. Naming of objects by dyslexic and other leamingdisabled children. Brain and Language, 3, l-15. Denckla, M. B., & Rude], R. G. 1976b. Rapid automatized naming (R.A.N.): Dyslexia differentiated from other learning disabilities. Neuropsychologia, 14, 471-479. Doehring, D. G., Trites, R., Pate& P., & Fiedorowicz, A. 1981. Reading disabilities: The interaction of reading, language, and neuropsychological deficits. New York: Academic Press. Dunne, L. M., & Dunne, L. 1981. Peabody Picture Vocabulary Test (rev. ed.). Circle Pines, MN: American Guidance Service. Ehri, L. C., & Wilce, L. S. 1985. Movement into reading: Is the first stage of printed word learning visual or phonetic? Reading Research Quarterly, 20, 163-179. Ellis, A. W. 1985. The cognitive neuropsychology of developmental (and acquired) dyslexia: A critical survey. Cognitive Neuropsychology, 2, 169-205. Ellis, A. W. 1987. On problems in developing culturally-transmitted cognitive modules: Review of P. H. K. Seymour, Cognitive analysts of dyslexia. London: Routledge & Kegan Paul. Mind and Language, 2(3), 242-251.

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