Processing of Derived Forms in High-Functioning Dyslexics

S. Hélène Deacon1, Rauno Parrila2, & John R. Kirby3

1 Dalhousie University, Halifax, Nova Scotia, Canada2 University of Alberta, Edmonton, Alberta, Canada

&3 Queen’s University at Kingston, Ontario, Canada

We report on an experiment designed to evaluate processing of derivedforms in high-functioning dyslexics, defined as university studentswith a history of reading difficulties who have age-appropriate readingcomprehension skills. We compared high-functioning dyslexics with agroup of normal adult readers in their performance on a lexical deci-sion task with derived items (such as cloudy and ably) and pseudo-derived items (such as belly and gravy). Some items contained anorthographic change (such as able-ably and gravy) and others didnot (such as cloud - cloudy). The results indicated that although con-trol participants’ response times varied systematically as a function ofmorphological complexity, those of high-functioning dyslexics did not.Further, there was some evidence of a relationship between deriva-tional processing and reading. It seems that high-functioning dyslex-ics have persistent difficulties in processing one particular aspect ofmorphology; that of derived forms.

Key Words: Derivational processing, high-functioning dyslexics, morphology, orthographic complexity,reading difficulties

A long line of research has demonstrated that phonologicalawareness is a key and causal factor in literacy development

Annals of Dyslexia, Vol. 56, No. 1, 2006Copyright ©2006 by The International Dyslexia Association®

ISSN 0736-9387

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(Bradley & Bryant, 1983; National Reading Panel, 2000).Certainly, children and adults with reading difficulties havemarked problems with the manipulation of sounds, orphonemes, within words (for reviews, see Morais, Carey,Alegria, & Bertelson, 1979; Snowling, 2000). These problemspersist in adults with a history of reading difficulties long afterthey have managed to achieve some level of competence intheir reading (e.g., Pennington, Van Orden, Smith, Green, &Haith, 1990; Snowling, Nation, Moxham, Gallagher, & Frith,1997). It is estimated that 22% to 25% of children with a diagno-sis of dyslexia will recover to the point that their adult readingis well within the normal range (Lefly & Pennington, 1991). Ofcourse, there is wide variation in the degree of such compensa-tion. The study reported here investigates “high-functioningdyslexics,” individuals with a history of reading difficultieswho have achieved a level of reading comprehension that per-mits their participation in postsecondary education. A keyquestion lies in how these individuals have been able to achievethis relatively high degree of competence in reading compre-hension despite well-established difficulties in phonologicalskills known to be so critical to reading outcomes. One possibil-ity is that high-functioning dyslexics have relatively strongmorphological processing skills that permit the compensationfor poor phonological processing skills (as suggested by Elbro &Arnbak, 1996). The evidence to date on this question can be de-scribed, at best, as mixed. The present study is designed to in-vestigate the morphological processing of derived forms inhigh-functioning dyslexics.

Morphemes are the smallest unit of meaning in language.The word uncovered, for example, is built out of the prefix un-,stem cover, and past tense suffix -ed. Several psycholinguisticmodels of the lexicon have proposed that affixes are “strippedoff” prior to lexical access (e.g., Taft & Forster, 1975) resulting infaster response times to real than to pseudo-derived words suchas unlike versus uncle, respectively (Rubin, Becker, & Freeman,1979; Taft, 1981). As a reaction against this proposal,Butterworth (1983) proposed a full-listing model in which mor-phologically complex words are represented in their entirety inthe lexicon (e.g., black, board, and blackboard each have separaterepresentations). The majority of current models take a compro-mise position, suggesting that there is a “race” between the twoprocessing (e.g., Marslen-Wilson, Tyler, Waksler, & Older, 1994;Taft, 1994). While the precise architecture of morphological or-ganization remains under investigation, there is good evidence

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that morphemes play a role in lexical access in the typical adultlexicon. Morphological effects in word recognition cannot be ac-counted for by orthographic or phonological similarities be-tween the items (e.g., Fowler, Napps, & Feldman, 1985; Napps& Fowler, 1987; Stoltz & Feldman, 1995) or by semantic overlapon its own (e.g., Bentin & Feldman, 1990; Feldman, 1992). Wewill build on this history of lexical access tasks in the investiga-tion of the consistency of derivational processing between high-functioning dyslexics and normal adult readers. To place such astudy within its broader context, we will review morphologicalprocessing as indexed by performance on a wide range of tasksby poor readers of all ages.

MORPHOLOGICAL PROCESSING IN YOUNG POOR READERS

We turn first to research that has contrasted the morphologicalskills of good and poor reading abilities. Giraudo (2001) com-pared priming effects from derived words (e.g., pottery - pot) tothose of pseudo-derived words (e.g., potato - pot). Although 8-year-old normally developing children were significantly fasterat recognizing words primed by morphological relatives, nosuch difference emerged in the dyslexic children. Similar evi-dence of morphological difficulties emerges in a study of oraland written production tasks. Rubin, Patterson, and Kantor(1991) found that learning disabled 7-year-olds lagged behindtheir peers in both oral and written morphological tasks.Parallel results emerged in the assessment of the use of mor-phology in word reading. Carlisle, Stone, and Katz (2001) foundthat 10- to 15-year-old readers were less accurate in their nam-ing and lexical decision responses for words with than withoutchanges in the phonology of the base form (e.g., natural and cul-tural, respectively), and these transformations were particularlyproblematic for the poor readers. Further evidence of impair-ments comes from Leong’s (1989b) finding that poor readers inGrades 4 to 6 were slower than their peers in reading wordspresented according to morphological rather than phonologicaldivisions (e.g., ACTor versus ACtor, respectively) (Taft, 1979),and in speed of production of base and derived forms to com-plete sentences (based on Carlisle, 1988; see Leong & Parkinson,1995 for similar results). Leong (1989a) further noted that out ofa large battery of measures, reaction times in the morphologicalproduction task were the best predictors of reading and spelling

ability within the poor reader group. The generation of baseforms with orthographic changes (e.g., generate begin from be-ginner) was particularly discriminative. Leong and Parkinson(1995) reported that similar delays in processing of derivedforms occur in repetition priming tasks. These results suggestthat the morphological processing of poor readers, as assessedacross a wide range of tasks with both accuracy and responsetime measures, lags at least behind that of their same age peers.

Certainly, morphology is not the only source of poor read-ers’ deficits. Fowler and Liberman (1995) found that 7- to 9-year-old poor readers had particular trouble with theproduction of derived forms involving phonological changes(e.g., heal - health) in comparison to their same age peers.Similarly, Shankweiler et al. (1995) showed that poor readersaged 7.5 to 9.5 years were impaired on both phonological andmorphological awareness tasks in comparison to chronologicalage controls. It appears that young poor readers are delayed onmorphological and phonological tasks in comparison to theirsame aged peers.

A number of researchers have advocated for the value of thereading level match design in studies of potential causal factorsin dyslexia (e.g., Goswami & Bryant, 1989; Jackson &Butterfield, 1989; Vellutino & Scanlon, 1989). Bourassa, Treiman,and Kessler (in press) recently used this approach to show thatdyslexic children were as likely as their younger, normally de-veloping peers to represent morphological information in theirspelling. Although it is widely agreed that results indicatingthat poor readers lag behind reading age matches can be a reli-able indicator of a potential causal variable in reading, the find-ing of no differences between poor readers and reading levelmatches (as in Bourassa et al., in press, among others) is far lessconclusive. Clearer evidence of difficulties comes from Joanisse,Manis, Keating, and Seidenberg’s (2000) work, which showedthat dyslexic children were poorer on tasks of productive inflec-tional morphology than controls with similar word identifica-tion skills. However, when the groups were equated on bothreading and phonological skills, the performances were similar.Joanisse et al. took this to reflect general language delays, in-cluding those in morphology, among the poor readers (seeCasalis, Colé, & Sopo, 2004 for similar findings in French).

In contrast, Carlisle and Stone (2003) showed that poorreaders’ use of morphology in reading was comparable to bothchronological and reading age matches. All three groupsshowed greater accuracy on derived than on pseudo-derived

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words (e.g., comparing hilly and silly, respectively). Reactiontime results were more ambiguous, perhaps reflecting tradeoffeffects (based on Tyler & Nagy, 1990). Further, Bryant, Nunes,and Bindman (1997) showed that although poor readers wereworse than age-matched controls in productive morphologicalawareness, they had somewhat better morphological awarenessthan reading age-matched controls. At the start of the longitudi-nal study, the poor readers were weaker in phonetic spellingand stronger in morphologically based spelling than a compari-son group with similar initial reading abilities (Bryant, Nunes,& Bindman, 1998). Bryant et al. described these results as indi-cating that poor readers have a “linguistic strength as well aslinguistic weakness” (1998, p. 509).

MORPHOLOGICAL PROCESSING IN ADOLESCENT POOR READERS

Shankweiler and colleagues’ research suggested that adolescentpoor readers have greater difficulties with morphological andphonological tasks in comparison to normal readers. Theyshowed that a group of 16-year-old learning disabled adolescentshad poorer productive and written morphological skills than 14-year-old normally developing readers (Shankweiler, Lundquist,Dreyer, & Dickinson, 1996). A more precise reading ability matchwas made by Carlisle (1987) in her comparison of 13-year-oldlearning-disabled children with normally developing childrenmatched on spelling abilities. The learning-disabled childrenwere more likely to spell only one member of a base-derived paircorrectly (and not consistently the base), suggesting that theywere more likely to represent multimorphemic words as wholewords. Findings of greater difficulties by poor readers than read-ing age matches indicate that morphological processing is a po-tential causal variable in reading difficulties.

As in the research with children, there is some suggestionthat morphological processing is, in fact, an area of strength foradolescent poor readers. Elbro and Arnbak (1996) showed thatdyslexic 15-year-old Danish students were faster at reading thecompound words than the control words (e.g., sunburn versuswindow), but that there was no such difference for the 9-year-oldreading comprehension age matched children. Further, the de-gree of increased speed of response time to the compounds wascorrelated with better reading comprehension, suggesting thatmorphologically based processing might offer a way for poor

readers to compensate for their phonological difficulties whilereading text. Further evidence of potential compensation comesfrom Elbro and Arnbak’s (1996) second study in which dyslexicadolescents were better than their younger peers in reading textparsed into morphemes rather than into syllables. These find-ings, like those of Bryant et al., suggest that morphology is anarea of relative strength that might permit poor readers to sur-pass some of the hurdles posed by poor phonological skills.

MORPHOLOGICAL PROCESSING IN ADULT POOR READERS

Rubin et al. (1991) found that adult dyslexics were similar to agroup of 7-year-old children (with whom they were notmatched on reading ability) in performance on morphologicalspelling, judgment, and production tests. Fischer, Shankweiler,and Liberman (1985) included a comparison group that wasmatched on reading abilities. They found that in comparison togood spellers of a similar age, poor adult spellers were insensi-tive to the morphemic composition of words. In contrast, Bruck(1993) showed that adult dyslexics had similar use of morphol-ogy in spelling in comparison to a group of younger readersmatched on reading comprehension, spelling, and word recog-nition. Leong (1999) found that adult dyslexics were slowerthan chronological age controls on timed phonological andmorphological tasks, and they were similar in performance toreading-ability matched controls. Thus, the vast majority of re-search on adult readers shows that they are similar to youngerindividuals with similar levels of reading in their use of mor-phology across a wide range of tasks.

THE PRESENT STUDY

The present study is designed to investigate the processing ofderived forms in high-functioning dyslexics, defined here asuniversity students with a history of reading difficulties whohave age-appropriate reading comprehension skills. Typically,high-functioning dyslexics demonstrate serious word level andreading rate difficulties, in addition to phonological processingdifficulties, while achieving age-appropriate levels of readingcomprehension specifically when tested in an untimed manner.Thus, it is commonly reported that they take longer than nor-

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mally achieving students to read material, and the most com-mon accommodation offered to them is longer time to completeassignments and tests.

The question of the most appropriate comparison group forhigh-functioning dyslexics is a difficult one. One approach in-volves finding younger individuals with similar word level ortimed reading comprehension abilities, as in the reading levelmatch design that is ideal for controlling reading experience toward the establishment of causal factors (e.g., Goswami &Bryant, 1989). Although this would achieve similarity on somereading ability dimensions, the groups would be substantiallydifferent in many other respects. For example, dyslexics in uni-versity and much younger readers would likely show a widegap in reading, educational, and world experience. Differencesin reading experience would be particularly problematic, as thisis the key control that the reading level match design is meantto accomplish. Further, even if it is possible to find groups withsimilar levels of print exposure in terms of the amount of textread, a vital assumption for the reading-level match designs, itis unlikely that the complexity of the texts read would be com-parable given that the high-functioning dyslexic group hasmade it to postsecondary education, and the control groups(from elementary or secondary schools) have not yet done so.Clearly, results from such comparisons could be misleading andthey would not help in identifying strengths, which is a keygoal of research with adult dyslexic samples. Another approachis to contrast high-functioning dyslexics with a group of normaladult readers with similar levels of untimed reading compre-hension. While such a comparison results in dyslexic and con-trol groups differing in word reading skills (and possibly intimed reading comprehension skills), it ensures a more similarreading (at least in terms of text complexity) and world experi-ence than using a younger word reading level control group.The present study adopted the second approach.

In addition, we focused specifically on processing of de-rived forms as assessed with a lexical decision task (Taft, 1979).In this task, participants decide if a letter string is a word andrespond accordingly with a button press, obviating the need fora spoken response. Rubin et al. (1979) found that participantsresponded faster to prefixed words than to pseudo-prefixed.These results parallel Carlisle and Stone’s (2003) findings ofgreater accuracy in reading derived than pseudo-derivedwords. Such comparisons offer a control for possible wordlength effects. To date, few studies have included equally com-

plex control words (Elbro & Arnbak, 1996; Giraudo, 2001; Rubinet al., 1991, are noteworthy exceptions), and poor readers mighthave difficulties with longer words in general rather than withmorphologically complex words in particular (see e.g., Ben-Dror, Pollatsek, & Scarpati, 1991; De Luca, Borrelli, Judica,Spinelli, & Zoccolotti, 2002; Nation, Marshall, & Snowling,2001). Longer words are often less frequent and require sublexi-cal processing, which might increase task demands that may af-fect dyslexic readers more than nondyslexic readers (e.g.,Parrila & Georgiou, 2005; van der Leij & van Daal, 1999; see alsoZoccolotti et al., 2005, for findings of word length effects forboth words and pseudowords). Lexical decision tasks also per-mit the use of a reaction time measure (the sensitivity of whichhas been advocated by many; e.g., Seidenderg, 1985; and em-ployed by even more; e.g., Leong, 1999), which may be particu-larly sensitive. We will use this comparison to address the statusof processing of derived forms in high-functioning dyslexics.

Based on Taft (1979) and others, we expected faster process-ing of derived than pseudo-derived forms by normal readerswhen the base is both phonologically and orthographicallytransparent. If morphological processing offers a compensatoryreading avenue into high-functioning dyslexics (as suggestedby Elbro & Arnbak’s 1996 study of compound word reading),then we would expect an even greater effect of derivationalstructure with the dyslexics than with the controls. Such a find-ing would suggest that derivational processing skills might per-mit an avenue of compensation in reading comprehension tosurpass phonological difficulties. A finding of a difference be-tween processing of derived and control words in the normals,but not in the high-functioning dyslexics would suggest that,just like phonological processing, derivational processing is anarea of weakness. The finding of similarity in derivational pro-cessing in the two groups would be ambiguous.

We were also interested in the role of orthographic complex-ity in derivational processing. It is clear that morphological pro-cessing operates independently of orthographic andphonological overlap (Fowler et al., 1985); specifically, evenwith words that share the same initial letters and sounds, thosefor which this initial section is a morpheme, offer greater prim-ing than those that do not (e.g., marking and market). However,in words in which there is a change in the orthographic repre-sentation (such as those investigated by Leong, 1989a) betweenthe base and the derived forms, morphological structure might,in fact, slow processing. Tyler and Nagy (1990) suggested that

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the reaction time gains accrued from the initial identification ofmorphological units might be offset by increased time to pro-cess these units. Orthographic changes between the derived andbase form are likely to bring about such tradeoffs (as have beenfound with phonological changes; e.g., Carlisle & Stone, 2003,2005). We will test whether this is the case in normal readersand compare their performance to that of high-functioningdyslexics. The status of orthographic knowledge is a particu-larly interesting one in relation to dyslexic samples as it hasbeen argued that it can be particularly strong in this group(Siegel, Share, & Geva, 1995). Further, as the results of Leong(1989a) suggested, derived forms involving orthographicchanges might be particularly indicative of reading difficulties.The measure of derived processing will include items with or-thographic changes to permit such an investigation.

Finally, we were interested in whether processing of derivedforms is related to reading ability in general. Elbro and Arnbak(1996) found that morphological processing was correlated withreading comprehension in their poor readers. They took this asevidence of morphological processing as a compensatory strat-egy in reading. We used the same approach to offer a secondway to determine the role that processing of derived formsplays in the relative level of reading achievement in high-functioning adult dyslexics.

METHOD

PARTICIPANTS

The high-functioning dyslexic group consisted of 27 partici-pants (nine males and 18 females) who reported a significanthistory of reading difficulties and whose performance on the el-ementary education section of the modified Adult ReadingHistory Questionnaire (Parrila, Corkett, Kirby, & Hein, 2003) in-dicated reading acquisition difficulties in childhood. Nine ofthem had recent diagnoses and had received or were receivingservices for learning-disabled students. The average age of thehigh-functioning dyslexic group was 30.08 (SD = 9.30; range 18to 52). The participants in the high-functioning dyslexic groupwere all either current university students or recent graduates(less than six months at the time of initial testing) and were re-cruited through letters sent by the university’s Student SupportServices, announcements in undergraduate classes, and postersdisplayed throughout the university’s campus.

The control group consisted of 28 participants (nine malesand 19 females) who reported no history of reading problems.The average age of the ND participants was 24.93 (SD = 6.31;range 18 to 49). The five-year difference in the mean ages ofthe groups resulted mainly from the dyslexic participants tak-ing a longer time after high school before enrolling in the uni-versity. The control group was recruited throughannouncements in undergraduate classes and through postersdisplayed throughout the university’s campus. All were cur-rent university students.

All participants reported English as their spoken languageof preference and normal or corrected to normal vision. As partof the testing, the participants completed a battery of readingand phonological processing tests. The reading tests consistedof computerized versions of Word Identification and WordAttack subtests from the Woodcock Reading MasteryTest–Revised (Woodcock, 1987) and of the Comprehension sub-test from the Nelson-Denny Reading Test (Brown, Fishco, &Hanna, 1993). The latter test provided two indices: reading rateand reading comprehension with a 20-minute time limit.Because of the time limit, many dyslexic participants did notanswer all the questions. To obtain an estimate of untimed read-ing comprehension ability, we also calculated the percentagecorrect of all attempted questions. The phonological processingtests were the Rosner Auditory Analysis Test (Rosner & Simon,1971), pseudohomophone choice (the participants had to choosebetween two nonwords the one that sounded like a real word),and rapid automatized naming (RAN) of digits (six digits—2, 7,4, 5, 3, and 8—presented five times each in a semirandom orderin a 4 x 9 matrix for the total of 36 stimuli) adapted from theComprehensive Test of Phonological Processing (Wagner,Torgesen, & Rashotte, 1999).

First, the performance of the high-functioning dyslexic par-ticipants with a recent diagnosis were compared to those with-out a recent diagnosis. The two groups did not differ in any ofthe measures (all ps > .171). Next, MANOVAs with the rawscores of the five reading variables, Wilks’ � =.522, F(5, 49) =8.99, p < .001, or the four phonological processing variables,Wilks’ � =.459, F(4, 50) = 14.71, p < .001, indicated that high-functioning dyslexic group was significantly different from thecontrol in their reading and phonological processing skills.Table I reports the means, standard deviations, and F-valuesfrom subsequent ANOVAs comparing the groups on readingand phonological processing tests. The two groups were signif-

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icantly different in both Word Identification and Word Attack;the high-functioning dyslexic group’s means reported in table Icorrespond roughly to grade equivalencies of 11 for WordIdentification and seven for Word Attack. We should note,however, that these tests were not presented in the standard-ized format.

The comprehension subtest of the Nelson-Denny ReadingTest was presented following the standard procedures and ac-cording to the norms, a reading rate scale score of 197 for thehigh-functioning dyslexic group represent an average level ofperformance in Grade 9 whereas their comprehension scalescore of 221 represents an average level of performance dur-ing the second year of university. In terms of end of the fourth

Table I. Means (and Standard Deviations) of Performance on the Readingand Phonological Processing Tests. F-values Report the Main Effect of

Group.

Group

Control High-functioning Dyslexics(n = 28) (n = 27)

Tests M M FReading

WRMT Word Identification 102.18 (2.86) 94.85 (6.22) 31.91***

WRMT Word Attack 38.61 (2.55) 32.96 (6.64) 17.53***

ND Rate 289.61 (94.80) 213.20 (98.62) 8.26**

ND Timed Comprehension 65.36 (8.42) 57.46 (12.58) 7.45**

ND Untimed Comprehension 89.68 (8.97) 86.00 (10.51) 1.95

Phonological Processing

AAT 36.54 (2.06) 30.48 (8.29) 14.06***

PC Accuracy 18.14 (1.76) 16.63 (3.56) 4.03*

PC Response Time 2.16 (0.56) 4.11 (1.49) 41.82***

RAN Digits 13.15 (3.14) 15.96 13.21**Note. WRMT = Woodcock Reading Mastery Test; ND = Nelson-Denny;

AAT = Rosner Auditory Analysis Test; PC = Pseudohomophone Choice; RAN= Rapid Automatized Naming.

* p < .05; ** p < .01; *** p < .001

year university norms, the control group’s reading rate corre-sponds to the 73rd percentile and comprehension to the 53rdpercentile, whereas the respective percentiles for the high-functioning dyslexic group are 27th and 29th. F values re-ported in table I show that the two groups were significantlydifferent in both reading rate and comprehension, but not inthe proportion correct measure that was calculated to esti-mate untimed reading comprehension and to adjust for thefact that many dyslexic participants did not finish the task in20 minutes. These results also suggest that our dyslexic par-ticipants continued to read text at a slower speed thannondyslexic university students, but they can understand textat an age appropriate level, particularly if given adequatetime. Further, it is important to note that timed comprehen-sion at the second year university level is age-appropriate byitself. In general, these results are similar to those of earlierstudies showing that university students with reading dis-abilities can perform similarly to normal readers on readingcomprehension tasks when the time constraints are removed(e.g., Mosberg & Johns, 1994), but they continue to struggleon decoding, word reading, reading speed, and phonologicalprocessing tasks (e.g., Aaron, 1989; Gallagher, Laxon,Armstrong, & Frith, 1996; Hatcher, Snowling, & Griffiths,2002; Rack, 1997).

MATERIALS

The derived items were made up of a base and a suffix (e.g.,read + er = reader). The pseudo-derived items were made up of asmaller word followed by a final letter-sequence that repre-sented a plausible morpheme (e.g., off + er = offer). In thepseudo-derived items, neither component was morphologicallyrelated. For the No Change derived items, there was no changein the sound, stress pattern, or orthographic representation be-tween the stem and the derived form (e.g., read - reader).Similarly, with the No Change pseudo-derived items, therewere no orthographic or phonological changes between thesmaller segment and the one-morpheme word (e.g., off - offer).For the Orthographic Change items, the smaller initial sectionof the words was spelled differently in the smaller and longerwords. This smaller word was the base morpheme for the de-rived items, but it was not for the pseudo-derived items (e.g.,able - ably and grave - gravy, respectively). As in Carlisle (1987,1988), these items included both changes in consonant doublingand in final letter spelling (e.g., fog - foggy and able - ably,

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respectively)1. There were eight items in each condition andthese are listed in the Appendix.

The frequency of the items and of the smaller word withinthe items (e.g., read in reader and off in offer) was balanced forKucera-Francis written frequency, obtained through the MRCpsycholinguistic database (ps > .76) (Coltheart, 1981). Words arealso similar in the number of letters and syllables (ps > .22). Theitems are listed in the Appendix.

PROCEDURE

The target items were embedded among 134 words and 104nonwords (88 pronounceable pseudowords and 16 letterstrings) in a standard lexical decision task in which the partici-pants were asked to press a button on a keyboard (RightControl for YES and Left Control for NO; buttons labeled ac-cordingly) to indicate if a letter-string was a word or not. Thewords and nonwords were matched on length, which varied be-tween four and 12 letters. They were presented in large blacktype (Times New Roman 42) in random order on the center of acomputer screen against a white background. The participantsfirst saw a fixation marker (a cross-hair) in the center of thescreen, followed by a word after 1000ms. The experiment gener-ation program (DirectRT v2004; Empirisoft, 1999-2004) recordedboth the reaction time and the accuracy of the response. Theparticipants were offered a short break after the first 125 items.

RESULTS

ANALYSIS OF LEXICAL DECISION TASK

Given very high accuracies and the ceiling effect in one cell (asshown in table II), accuracy data were not analysed further.Mean accuracy for any one item did not drop below .52, withthe majority above .90. Reliability analyses of the eight itemswithin each condition show reasonable reliability (alphas > .7).

Response times to correctly responded items in each condi-tion by each participant group are shown in table II. Data werecleaned so that response times faster than 200 ms or slower than

1. There were two Orthographic Change items that included slight phonologi-cal changes (center - central; able - ably). These were included because of the dif-ficulty in locating items that met all of the criteria for balancing. The highlevels of reliability (reported in the Results section) suggests that there weresimilarities in processing across the set of Orthographic Change items.

3000 ms were removed, as were outliers (defined as responsetimes more than two standard deviations from the mean re-sponse time for a given individual in that condition). Data wereanalysed with a repeated-measures ANOVA with Change Type(No Change or Orthographic Change), Word Type (Derived orPseudo-derived), and Group (Normal or High-functioningDyslexic) as factors in the analyses by subjects. Results are re-ported for analyses by subjects (F1) and by items (F2).According to Raaijmakers, Schrijnemakers, and Gremmen(1999), in experiments with highly selected items such as thisone, only significance in the analyses by subjects is required toreject the null hypothesis.

Analyses suggest that there are differences between the twogroups of participants. There was a trend for faster responsetimes for the control group than for the dyslexic group, F1(1, 53)= 3.417, p = .070; F2(1, 28) = 32.826, p < .001.

Most critically for the questions at hand, it appears thatthere are differences between the groups in their derivational

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Table II. Mean Response Time and Standard Deviation (in parentheses) toRespond to the Lexical Decision Task.

High-functioningWord Type Control Dyslexics

Response time to correctNo Change

Derived 718 (171) 838 (218)

Pseudo-derived 793 (177) 851 (261)

Derivational Sensitivity .900 (.198) .985 (.187)

Orthographic Change

Derived 899 (261) 927 (291)

Pseudo-derived 705 (128) 885 (284)

Derivational Sensitivity 1.28 (.296) 1.047 (.197)

AccuracyNo Change

Derived 1.00 (.00) .83 (.12)

Pseudo-derived .98 (.04) .97 (.08)

Orthographic Change

Derived .92 (.10) .98 (.06)

Pseudo-derived .99 (.03) .94 (.09)

DERIVED FORM PROCESSING IN HIGH-FUNCTIONING DYSLEXICS 117

processing. A main effect of Change Type (F1[1, 53] = 8.307, p =.006; F2[1, 28] = 2.283, p = .142), and significant interactions be-tween Word Type and Change Type (F1[1, 53] = 18.011, p < .001;F2[1, 28] = 5.716, p = .024) and between Word Type, ChangeType, and Group (F1[1, 53] = 7.947, p = .007; F2[1, 28] = 6.592, p = .016).

Analyses of the two-way interaction showed that responseswere faster for the derived than for the pseudo-derived items inthe No Change condition (t1[54] = 2.453, p = .017; F2[1, 14] =0.829, p = .378) at a level that was slightly above the Bonferronicorrected p-value (p < .0125). In contrast, response times wereslower for the derived than for the pseudo-derived items in theOrthographic Change condition (t1[54] = 2.989, p = .004; F2[1,14] = 4.705, p = .048). These results indicate that the effect ofmorphological structure on the processing of derived formschanged as a function of the type of change between the baseand derived form: speeding processing of items without achange in the orthographic representation of the base and slow-ing processing of items with this change. The effects of ortho-graphic structure also varied across derived andpseudo-derived conditions, showing a significant slowing of re-action times for the derived items (t1[54] = 3.743, p < .001; F2[1,14] = 4.165, p = .061), but not for the pseudo-derived items(t1[54] = 1.261, n.s.; F2[1, 14] = 0.967, n.s.).

Analyses of the three-way interaction showed that for thecontrol group, there were main effects of both Word Type (F1[1,27] = 4.832, p = .037; F2[1, 28] = 2.229, p = .147) and Change Type(F1[1, 27] = 4.344, p = .047; F2[1, 28] = 1.642, p = .221), indicatingthat response times were slower for Orthographic than for NoChange items, and for pseudo-derived than for derived items.These main effects were qualified by an interaction betweenWord Type and Change Type (F1[1, 27] = 26.728, p < .001; F2[1,28] = 9.382, p = .005). Follow-up paired-sample t-tests of the in-teraction focused on the effects of derivational structure withinthe No Change and Orthographic Change items, respectively, asthis was the primary focus of the experiment. Control partici-pants were faster with the derived than with the pseudo-derived items (t1[27] = 2.579, p = .016; F2[1, 14] = 2.090, p = .170)for the No change items. In contrast, responses were faster tothe pseudo-derived than to the derived items for theOrthographic Change items (t1[27] = 3.992, p < .001; F2[1, 14] =7.359, p = .017). If the interaction is examined according to theeffects of orthographic structure, we see that there are effects oforthographic change far more robust for the processing of

derived (t1[27] = 4.535, p < .001; F2[1, 14] = 6.337, p = .025) thanfor the pseudo-derived items (t1[27] = 2.233, p = .034; F2[1, 14] =1.712, p = .212). The critical finding here is that the controlgroup’s response times were clearly affected by the derivationalstructure of the presented items.

In contrast, for the high-functioning dyslexic group, onlyone effect approached significance; response times tended to beshorter for the No Change items than for the OrthographicChange items (F1[1, 26] = 4.118, p = .053; F2[1, 28] = 2.482, p =.126). This effect also appeared for the control group, indicatingthat both groups found the words involving orthographicchanges difficult to process (no interaction between ChangeType and Group, p > .25). However, unlike the control group,the lack of an interaction with Word Type indicates that this ef-fect held for both the derived and pseudo-derived words for thehigh-functioning dyslexic group.

In sum, the control group participants benefited from mor-phological complexity when the relationship between the baseand derived form was transparent as in No Change condition.When the relationship was less transparent, morphologicalcomplexity resulted in slower response times. High-function-ing dyslexics, in contrast, showed no effects of morphologicalcomplexity.

DERIVATIONAL PROCESSING AND READING

To assess the relationship between derivational processing andreading, we first calculated two indices of derivational sensitiv-ity for each participant (based on Elbro & Arnbak, 1996). Theseindices were calculated with the reaction time to correctly iden-tify items. We divided this reaction time for the items in the de-rived condition by that for the pseudo-derived condition itemsfor each of the No Change and Orthographic Change condi-tions, respectively (resulting in two indices reported in table II).These offer an index of how much the individual was speeded(or slowed, as the case may be) by added morphological com-plexity. The calculation of these indices for each individual al-lows the evaluation of correlations across the two samplegroups combined together, alleviating concerns regarding re-duced sample sizes and power associated with the splitting ofgroups.

We calculated correlations between these two measures ofderivational sensitivity and the reading measures (reported intable III). If derivational processing is linked to reading, thenthere should be relationships between the derivational sensitiv-

118 DEACON, PARRILA, AND KIRBY

DERIVED FORM PROCESSING IN HIGH-FUNCTIONING DYSLEXICS 119

ity measures and reading. Positive correlations indicate that bet-ter readers read derived words faster than pseudo-deriveditems. We found that derivational sensitivity to No Changeforms was significantly related to word identification andderivational sensitivity to Orthographic Change forms was re-lated to timed reading comprehension at a significant level andto word identification at a level approaching significance (p =.061). The relationships between processing of the No Changeforms and reading variables are negative, reflecting the fact thatprocessing is speeded in the derived as compared to thepseudo-derived condition, while those between OrthographicChange forms and reading are positive, reflecting the slowingof processing in the derived condition.

We also calculated these correlations separately for bothsamples in the study (reported in table IV). These within-groupcorrelations show that only the relationship between deriva-tional sensitivity to Orthographic Change forms and timedreading comprehension remained at a level approaching signifi-cance in the control group (p = .057). There were no such trendsin the high-functioning dyslexics.

DISCUSSION

The current experiment was designed to investigate deriva-tional processing in high-functioning dyslexic adults. We com-pared individuals with a history of reading difficulties who

Table III. Correlations between Indices of Derivational Sensitivity (DS) forthe No Change and Orthographic Change Conditions and Reading

Measures.

1. 2. 3. 4. 5.1. D.S. No change

2. D.S. Orth. Change -.149

3. Reading rate .026 .185

4. Untimed Reading Comp. .007 .248 .139

5. Timed Reading Comp. -.076 .339* .421** .676***

6. Word Identification -.295* .254† .238† .194 .472***Note. † indicates p < .10, * p < .05, ** p < .01, *** p < .001.

were participating in postsecondary education with normalreaders. High-functioning dyslexics were poorer than the con-trol group on a range of phonological processing and readingtasks, although they had comparable levels of untimed readingcomprehension. We found striking differences in response timepatterns to morphologically complex words between normalreaders and high-functioning dyslexics. While the controlgroup’s response times varied according to the morphologicalcomplexity of the words that they encountered, those of thehigh-functioning dyslexics did not.

The results added to the existing evidence for a morphologi-cally mediated route for the identification of derived words inthe lexicon in normal readers as suggested in several models oflexical access. It seems that for the normal readers, morphologi-cal structure speeds the recognition of derived words with nochange in orthographic structure from base to derived form.This finding replicates previous lexical decision results (e.g.,Taft, 1981). In contrast, when the words involved orthographicchanges (such as between able and ably), responses were slowerto derived than to pseudo-derived words. The effects of thechange in orthographic structure were most robust for the de-rived items, both in the analysis of two groups together and in

120 DEACON, PARRILA, AND KIRBY

Table IV. Correlations between Indices of Derivational Sensitivity (DS) forthe No Change and Orthographic Change Conditions and Reading

Measures for the Control Group Below the Diagonal and for the High-Functioning Dyslexics Above.

1. 2. 3. 4. 5. 6. 1. D.S. No change -.118 .290 .028 .053 -.236

2. D.S. Orth. Change -.025 .174 .047 .143 -.049

3. Reading rate -.027 -.020 .113 .341† -.093

4. Untimed Reading Comp. .087 .317 .075 .609** .134

5. Timed Reading Comp. -.049 .364† . 349† .767*** .358†

6. Word Identification -.133 .125 .241 .037 .326†Note. † indicates p < .10, * p < .05, ** p < .01, *** p < .001.

DERIVED FORM PROCESSING IN HIGH-FUNCTIONING DYSLEXICS 121

the analysis of the normal readers’ data on its own, suggestingthat the slowing effects of orthographic changes are relativelyspecific to derivational access processes. This type of detrimen-tal effect of morphological complexity has been found in otherinvestigations, as in the time-consuming recombination ofwords with high frequency bases (Taft, 2004) and the rejectionof nonwords with morphologically plausible components(Caramazza, Laudanna, & Romani, 1992). To our knowledge,the “costs” associated with recognizing multimorphemic wordswith complex orthographic structures have not been previouslyidentified. This finding is consistent with Tyler and Nagy’s(1990) proposal of a timing tradeoff between access to and pro-cessing of morphemes within some morphologically complexwords, as well as Taft and Forster’s (1975) suggestion that theprocessing of certain types of morphologically complex wordscan be effortful and time-consuming.

In contrast to this sensitivity of normal readers to deriva-tional structure, the high-functioning dyslexics in this study didnot demonstrate any such appreciation. Response times did notdiffer between the pseudo-derived and derived words in eitherthe No Change or the Orthographic Change condition. This nullresult resonates with findings from Giraudo (2001), suggestingthat individuals with reading difficulties do not demonstratesensitivity to morphological structure in time-sensitive tasks.Findings from this experiment extend these results to a newgroup, that of high-functioning dyslexics, at least within the do-main of derivational processing. It may be that this group hadearly difficulties in accessing the morphemic structure of de-rived forms and that remnants of these difficulties remain, as dotheir phonological difficulties. At first glance, the finding thatresponse times for this group were not slowed by the ortho-graphic complexity of the base forms of the derived words withorthographic changes might appear to be evidence of a relativemorphological or orthographic strength. However, theOrthographic Change derivational sensitivity index was posi-tively related to reading abilities in the analyses across all par-ticipants and in the normal adult reading group alone, showingthat this slowing of response time by orthographic complexitywas related to efficient decoding and comprehension of text.These results do not support the existence of the orthographicstrength suggested by Siegel et al. (1995). Further, this link toreading is reminiscent of Leong (1989a), who found that itemswith orthographic changes were particularly indicative of read-ing and spelling difficulties. Although these findings clearly

need to be replicated with a wider range of items, the differ-ences in the processing of derived words uncovered in this ex-periment have implications for the interpretation of previousstudies indicating that high-functioning dyslexics read words ina qualitatively similar manner to that of normally developingreaders (e.g., Ben-Dror et al., 1991; Watson & Brown, 1992). Ourresults suggest that, when faced with derived words, high-functioning dyslexics may approach words differently than nor-mal readers (see also Leong, 1999).

The finding that sensitivity to the structure of derivedwords, as assessed in the lexical decision task, is related to read-ing performance is worth some consideration. In the analyseswith all participants, the derivational sensitivity index in the NoChange condition was significantly related to word identifica-tion, and there was a trend toward such a relationship with theOrthographic Change derivational sensitivity index. Sensitivityto derived forms with orthographic changes was also related totimed reading comprehension and there was an appropriatetrend in the analysis of the normal sample on its own. These re-sults resonate with those of Leong (1989a), and they providesome evidence that derivational processing is a component ofaccurate decoding of words and efficient comprehension of textin normal adult readers. Clearly, there was no such relationshipin the high-functioning dyslexics’ data, suggesting that a poten-tial normal relationship between derivational processing andreading was not intact in this group. Although lexical decisiontasks have been used extensively to investigate a wide range ofmorphological processing in adults, we are not aware of anypublished reports that have attempted to relate such measuresto reading ability in adults. While this study provides some firstevidence for a relationship, it requires further investigation, in-cluding a more thorough coverage of morphological processingand reading tasks. Future studies could investigate possible in-teractions between morphological processing and other factors(e.g., phonological complexity and word length) that haveshown to be important.

One of the hypotheses that we wanted to explore waswhether morphology offered a compensatory mechanismthrough which high-functioning dyslexics might have achievedsome degree of reading comprehension, albeit slow. This was aplausible hypothesis, given the results of prior research (e.g.,Elbro & Arnbak, 1996). Our results indicate that unlike normaladult readers, high-functioning dyslexics do not demonstratesensitivity to derivational morphology within this timed word

122 DEACON, PARRILA, AND KIRBY

DERIVED FORM PROCESSING IN HIGH-FUNCTIONING DYSLEXICS 123

recognition task. These findings emerged in a comparison oftwo groups with similar levels of untimed reading comprehen-sion and these results clearly need to be replicated with a groupwith similar word reading skills. Nevertheless, the present re-sults make it unlikely that this derivational processing is an areathrough which these individuals might have compensated forreading difficulties, at least not in a manner that permits themto increase their reading speed. The majority of earlier researchemployed untimed production tasks, either oral or written. It ispossible that children and adults with reading difficulties canuse morphology to generate words and spellings in tasks forwhich there is no time limit, but they cannot do so in an effi-cient manner. Response times of the high-functioning dyslexicswere slower than those of controls across all conditions in thelexical decision task, suggesting that this task is more cogni-tively demanding for this group than for control participants.Increased task demands might have interrupted the normal re-lationship between derivational processing and reading, a linkfor which we found some emerging evidence. The comparisonof timed and untimed tasks in new studies would permit the in-vestigation of this possibility. It is also possible that it is specifi-cally the semantic aspect of morphology that permits poorreaders to use this strategy. Compound words, such as those in-vestigated in Elbro and Arnbak (1996), have a high level of se-mantic transparency, and poor readers might be able to use acompensatory morphological strategy with forms with salientmeanings (as suggested by Elbro, 1990). Further research needsto explore the extent of morphological abilities in tasks with awide range of morphemes, as well with varying response de-mands and semantic salience.

Further research should also investigate the performance ofhigh-functioning dyslexics in comparison to different types ofcontrol groups. In this experiment, we contrasted two groups ofadult readers with similar levels of untimed reading compre-hension. This is a potentially useful approach in the identifica-tion of strengths of dyslexic readers. However, there was arange of differences between these two groups, including per-formance on phonological and word reading measures. Withadult dyslexics, it may be impossible to find a true controlgroup, one that differs in only one feature from the targetgroup. The only pragmatic solution may be to include differenttypes of comparisons in separate studies to control for variouscritical features in separate studies. For example, high-functioningdyslexics could be compared to much younger individuals with

similar levels of phonological and single-word reading abilities.Although these groups might not have comparable reading ex-perience levels (given the wide difference in age of the partici-pants), they would be similar in underlying processing skills.

This experiment set out to evaluate derivational processingin high-functioning dyslexics, a question that has not been ad-dressed to date in experimental research. We did not find evi-dence of sensitivity to derivational morphology in a timedlexical decision task within this specific adult sample; the nor-mal readers’ response times to derived and pseudo-derivedwords varied systematically as a function of morphologicalcomplexity, but those of high-functioning dyslexics did not.Further, there was evidence of a relationship between deriva-tional processing and reading, a finding that requires further ex-ploration. There was some indication that this link existedprimarily for the normal readers. In summary, high-functioningdyslexics may have persistent difficulties in derivational pro-cessing, especially in timed tasks. Future research needs to ex-plore the interaction between linguistic processing abilities in arange of domains, including morphological and phonological,in this group.

Address correspondence to: S. Hélène Deacon, Departmentof Psychology, LSC, Dalhousie University, 1355 Oxford Street,Halifax, Nova Scotia, Canada, B3H 4J1. Phone: (902) 494-2538;Fax: (902) 494-6585; E-mail: sdeacon@dal.ca

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APPENDIX

FREQUENCIES OF THE TARGET WORDS AND FIRST SEGMENTS OF THE TARGET WORDS

Derived No Change Words Pseudo-derived Control Wordsship 83 shipment 2 bread 41 breadth 7

dirt 43 dirty 36 apart 57 apartment 81

dust 70 dusty 16 top 204 topic 9

music 216 musical 85 bell 18 belly 23

farm 125 farmer 23 met 132 metal 61

read 173 reader 43 wit 20 witness 28

paint 37 painter 21 pan 16 panic 22

cloud 28 cloudy 2 ten 165 tenant 5

Mean 96.88 28.50 96.88 28.50

Derived Orthographic Pseudo-derivedChange Words Control Words

center 224 central 164 ham 19 hammer 9

fog 25 foggy 5 war 464 warrant 20

fun 44 funny 41 cop 15 copper 13

begin 84 beginner 34 gut 1 gutter 1

able 216 ably 2 grave 33 gravy 4

bag 42 baggy 4 lad 6 ladder 19

cool 62 coolly 5 ban 7 banner 8

chop 3 choppy 3 let 384 letter 145

Mean 87.50 32.25 116.13 27.38

128 DEACON, PARRILA, AND KIRBY