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Neuropsychologia 44 (2006) 2861–2873

Phonological dyslexia and phonological impairment:An exception to the rule?

Jeremy J. Tree ∗, Janice KayUniversity of Exeter, United Kingdom

Received 5 January 2006; received in revised form 6 June 2006; accepted 7 June 2006Available online 1 August 2006

bstract

The condition known as phonological dyslexia involves very poor reading of non-words, with otherwise good word reading performance [e.g.erouesne & Beauvois, 1979; Sartori, G., Barry, C., & Job, R. (1984). Phonological dyslexia: A review. In R. N. Malatesha & H. A. Whitaker (Eds.),yslexia: A global issue. The Hague: Martinus Nijhoff Publishers]. Theoretical accounts of this non-word reading impairment suggest disruption

o either a component of a non-lexical orthographic-phonological reading route [that is specifically involved in reading non-words; Coltheart, M.,astle, K., Perry, C., Langdon, R., & Zeigler, J. (2001). A dual route cascaded model of visual word recognition and reading aloud. Psychologicaleview, 108, 204–256] or to generalised phonological processes on which novel reading is heavily dependent [Farah, M., Stowe, R. M., & Levinson,. L. (1996). Phonological dyslexia: Loss of a reading-specific component of cognitive architecture? Cognitive Neuropsychology, 13, 849–868;arm, M. W., & Seidenberg, M. S. (1999). Phonology, reading acquisition, and dyslexia: Insights from connectionist models. Psychological Review,06, 491–528]. The present paper questions the latter hypothesis: that phonological dyslexia always occurs in connection with some other form ofhonologically based disruption (i.e. in a ‘cluster’ of impairments that are not necessarily reading-specific). Contrary to this view, several recenttudies have reported that phonological dyslexia can occur without corresponding generalised phonological impairment [e.g. Caccappolo-vanliet, E., Miozzo, M., & Stern, Y. (2004a). Phonological dyslexia without phonological impairment? Cognitive Neuropsychology, 21, 820–839;accappollo-van Vliet, E., Miozzo, M., & Stern, Y. (2004b). Phonological dyslexia: A test case for reading models. Psychological Science, 15,83–590]. However, the work is subject to a number of criticisms. The following study examines performance of a phonological dyslexic case (JH)n a variety of phonological based tasks and, unlike many other studies, components of phonological short-term memory. Despite clear impairments

n reading non-words, good performance on a variety of phonological tasks makes the possibility of generalised phonologically based disruptionnlikely. The view that JH’s good phonological skill was dependent on the use of spelling based strategies was also excluded. As a result, JH’sattern of performance provides clear evidence that phonological dyslexia can occur without any generalised phonological impairment.

2006 Elsevier Ltd. All rights reserved.

Cv1au

eywords: Phonological; Dyslexia

. Introduction

Phonological dyslexia is an impairment of reading novelords (non-words) with otherwise good performance in reading

amiliar words (see Sartori, Barry, & Job, 1984, for a review).

lthough this condition has been widely documented in theeuropsychological literature in both acquired and developmen-al cases (e.g. Berndt, Haendiges, Mitchum, & Wayland, 1996;

∗ Corresponding author at: Washington Singer Laboratories, School of Psy-hology, University of Exeter, Perry Road, Exeter, Devon EX4 4QG, Unitedingdom. Tel.: +44 1392 264693; fax: +44 1392 264623.

E-mail address: J.TREE@Exeter.ac.uk (J.J. Tree).

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028-3932/$ – see front matter © 2006 Elsevier Ltd. All rights reserved.oi:10.1016/j.neuropsychologia.2006.06.006

accappolo-van Vliet, Miozzo, & Stern, 2004a; Caccappolo-an Vliet, Miozzo, & Stern, 2004b; Derouesne & Beauvois,979; Funnell, 1983; Patterson, 1982) there is considerable dis-greement about the nature of the functional impairment thatnderlies poor non-word reading. Early accounts of phonolog-cal dyslexia were based on a ‘dual-route’ model of readingModel A—see Fig. 1), in which non-words are read exclusivelyy using a non-lexical rule governed and piecemeal methodf mapping orthographic information (graphemes) to phono-ogical information (e.g. Coltheart, Curtis, Atkins, & Haller,

993). This account for poor non-word reading was thereforetraightforward; it must occur as a consequence of damage to theon-lexical route (since it is required to enable reading aloud ofll novel words), with relative sparing of a separate lexical read-

2862 J.J. Tree, J. Kay / Neuropsychologia 44 (2006) 2861–2873

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Fig. 1. Model A: The dual-route cascaded (DRC) model of reading

ng route (e.g. Derouesne & Beauvois, 1979). In recent times,his account has been outlined in a computational model knowns the ‘dual-route cascaded model’ (DRC, Coltheart, Rastle,erry, Langdon, & Zeigler, 2001), with phonological dyslexiaccurring as a result of disruption to the grapheme–phonemeorrespondence system (labelled A in Fig. 1), such that somespect of this mechanism is disrupted. In fact using this compu-ational model, Coltheart et al. (2001) successfully simulated theon-word reading impairment seen in two phonological dyslex-cs (LB—Derouesne & Beauvois, 1985; Melanie-Jane – Howard

Best, 1996) by increasing the parameter, which determines theumber of cycles it takes before moving onto the next letter insequence. In effect, this manipulation to the model captured

he proposal that poor non-word reading reflects the very weakctivation of an otherwise normal non-lexical route. Neverthe-ess, despite the fact that this relatively simple manipulation haseen successful in modelling previous published cases of phono-

ogical dyslexia, this is by no means the only way a non-wordeading impairment could be potentially simulated.

However, an alternative explanation suggests that phonolog-cal dyslexia is not a reading disorder per se, but occurs as a

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: A, non-lexical reading route; B(i) and B(ii), lexical reading route).

esult of disruption to phonological processes on which novelord reading is dependent. This is clearly illustrated in connec-

ionist models in which no non-lexical reading route is assumede.g. Harm & Seidenberg, 1999, Harm & Seidenberg, 2001),nd is also the basis for the view that, as reading is a rela-ively ‘new’ functional process in evolutionary terms, it mustherefore be parasitic in some sense on existing phonologi-al systems (Farah, Stowe, & Levinson, 1996). In line withhis view, a majority of case reports of phonological dyslexiaincluding all 17 cases reported in a special issue of Cog-itive Neuropsychology in 1996) have been shown to haveubtle to severe phonological impairments. The present studyddresses this ‘phonological impairment’ hypothesis of phono-ogical dyslexia. We examine the performance of a neurologicalatient, JH, who presents with acquired phonological dyslexia,esting his ability on a variety of tasks that appear to tap both gen-ralised phonological processing and phonological short-term

emory. In this way, we have sought to determine whether

is non-word reading impairment occurs in isolation or inonjunction with an additional phonologically based impair-ent.

J.J. Tree, J. Kay / Neuropsychologia 44 (2006) 2861–2873 2863

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ig. 2. Model B: The ‘triangle’ model (Note: A, O → S → P pathway; B, O → P

.1. Phonological dyslexia and the ‘triangle’ model ofeading

In a series of connectionist simulations that are oftenollectively referred to as the ‘triangle’ model of readingHarm & Seidenberg, 2001; Harm & Seidenberg, 2004; Plaut,

cClelland, Seidenberg, & Patterson, 1996), it is proposed (seeig. 2) that non-words, along with words, are read aloud byprocess that involves direct and dynamic connections from

rthography to phonology. As is apparent from Fig. 2, this modelffectively posits two types of reading pathway, one that involvesemantic representations (the O → S → P pathway, marked A inig. 2) and the other which does not; given non-words have noeaning it is assumed that they heavily dependent on the ‘direct’

onnections between orthography and phonology (referred to ashe O → P pathway marked B in Fig. 2).

In an early non-connectionist conception of such a model,riedman (1995) argued that an impairment of reading non-ords could occur as a result of two possible loci of damage: (1)

mpairment to phonological representations; (2) impairment ofirect connections between orthography and phonology (O → Ponnections see pathway B in Fig. 2)1; Friedman (1995) arguedhat impairment of phonological representations may stem from:a) a problem with generating an internal abstract phonologicalode (i.e. within phonological representations), or (b) a prob-em with maintaining such codes in auditory-verbal short-term

emory (note that while this can be characterised in terms ofmpairment to a ‘phonological output buffer’, this does not con-titute part of the architecture of the triangle model). A third

1 It is important to note that the schematic model refers to a number of dif-erent simulations that have examined particular patterns of acquired readingmpairment (Hinton & Shallice, 1991; Plaut & Shallice, 1993, deep dyslexia;atterson, Seidenberg, & McClelland, 1989; Plaut et al., 1996, surface dyslexia;arm & Seidenberg, 2001, phonological dyslexia). However it remains to be

een if all these reading impairments can be adequately simulated in a singlenified model (Harm & Seidenberg, 2004).

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ay; each oval corresponds to a set of units and arrows denote interconnections).

ossibility, not explicitly stated by Friedman (1995) is that thehonological impairment may reflect a combination of (a) andb).

On the basis of the proposals of (1) and (2) above, Friedman1995) puts forward two quite different case profiles that maye observed in phonological dyslexia. Cases with an impairmentf subtype (1) should show a generalised disruption of phono-ogical processing, reflected by poor performance in a variety ofasks that are highly dependent on such processes, including dif-culties in reading aloud non-words. Thus, these cases would bexpected to perform poorly on tasks that involve the manipula-ion of phonology, such as segmentation (e.g. say ‘Cat’ withouthe first or last phoneme) or blending (e.g. /h/ + /æt/ = ?). Exam-les of such documented cases include, KT (Patterson, Suzuki,

Wydell, 1996), and the five cases (WBA, BBO, DPR, RTInd TWA) documented in Patterson and Marcel’s (1992) sem-nal paper that was the first to suggest a causal link betweenhonological impairment and non-word reading impairment. Invariant of subtype (1), one would also expect to observe cases ofhonological dyslexia that are characterised by poor auditory-erbal short-term memory performance. Disruption to mech-nisms implicated in the maintenance of phonological codesdescribed as, for example, an impairment of a phonologicalutput buffer), have been held to account for the reading perfor-ance of RR (Bisiacchi, Cipolotti, & Denes, 1989), ML (MartinLesch, 1996) and MS/BR (Friedman, 1996). The latter two

ases also presented with specific problems reading words inext (referred to as ‘phonological text alexia’). Most recently,arm and Seidenberg (2001) argued on the basis of their ‘tri-

ngle’ model, that non-words are more likely to be impairedhan words in cases of phonological disruption in phonologicalyslexia because they do not activate the semantic system, ando not have well established connections between orthography

nd semantics (as words do) which can further support phono-ogical activation. These two factors make non-word retrievalless stable process. In an earlier paper, Harm and Seidenberg

1999) simulated patterns of performance seen in developmental

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864 J.J. Tree, J. Kay / Neuropsy

honological dyslexia, by disrupting their model in two ways: (a)ild phonological impairment (simulated by a slight degree ofeight decay on phonological feature units throughout training);

b) moderate phonological impairment (in addition to weightecay, clean-up units were removed, as were 50% of intercon-ections between phonetic feature units). In sum, their version ofhe ‘triangle’ model appeared to be able to mimic the impairmenteen in developmental phonological dyslexia on the basis of spe-ific disruption to phonological units, indicating that generalisedhonological disruption appeared to be sufficient to account forhe poor non-word reading performance seen in these cases.

According to Friedman (1995), cases with an impairmentf subtype (2) would be highly dependent on reading via theemantic pathway (namely the O → S → P pathway marked An Fig. 2), and therefore will show varying levels of word readinguccess, dependent on the strength or richness of correspondingemantic representations. Words with little associated seman-ic/conceptual information (such as many function words), andf course non-words, should therefore be read with less suc-ess than those with a great deal (such as concrete nouns). It ispparent that under Friedman’s (1995) proposals cases of thisecond type would not necessarily present with a generalisedhonological impairment, but one would expect to see associ-ted difficulties in comprehension and reading aloud of functionords. It is of note that despite these initial proposals, subse-uent computational work using versions of the ‘triangle’ modeluggested that simulating poor non-word reading under thisecond impairment subtype is problematic. Plaut et al. (1996)referred to explain the pattern of performance in the phonologi-al dyslexic cases they considered with reference to the ‘triangle’odel using a generalised phonological impairment account,

cknowledging that an O → P account (i.e. Friedman’s subtype2) account) would be difficult to undertake. In later work, Harmnd Seidenberg (2001) also rejected this second account as beingeasible using their computationally implemented version of thetriangle’ model’, given that under their simulations disruptionf the O → P pathway resulted in impairment of both non-wordnd irregular word accuracy (for similar conclusions see Harmnd Seidenberg (2004)). As a result, we would conclude thatlthough under Friedman’s (1995) early conception of a ‘trian-le’ model (i.e. a model with no non-lexical reading route) therere two possible accounts of how a phonological dyslexic pat-ern of impairment may occur, on the basis of the most recentomputationally implemented versions of the ‘triangle’ modelhe second of these two possible accounts (namely a disruptionf the O → P pathway) is unlikely to be realised. As a result, theresent work will focus on the ‘generalised phonological impair-ent’ account of phonological dyslexia in an effort to scrutinise

he feasibility that the ‘triangle’ model can adequately accountor the pattern of impairment seen in our own case.

.2. Phonological dyslexia—specific non-word readingmpairment or generalised phonological disorder?

Earlier we pointed out that the majority of cases of phono-ogical dyslexia appear to have both a specific non-word readingmpairment coupled with a more generalised phonological dis-

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gia 44 (2006) 2861–2873

rder. However, there have been several reports of phonologicalyslexia that directly challenge this pattern. Several recent stud-es have reported preserved phonological processing, in the con-ext of impaired non-word reading (e.g. Caccappolo-van Vliett al., 2004a,b) and well-preserved word reading, including ofunctors. However, it is important to ensure that all potentialccounts (impaired phonological processing, impaired audi-ory verbal short-term memory, impaired word/functor reading)re excluded. And to do this convincingly, information shoulde gathered on a common series of phonological tasks, tap-ing both general phonological processing and output buffermpairment, and on function word reading and comprehension.nfortunately, on re-examination, many previous studies have

ailed to provide this information comprehensively. For exam-le, Caccappolo-van Vliet et al. (2004a,b) provide strong evi-ence that their cases (RG, MO and IB) have no apparent impair-ents on tasks of phonological processing (e.g. phonological

egmentation/deletion and blending). However, as all of theases had severe auditory verbal short-term memory and someomprehension impairments, no further testing could be under-aken, with the result that a short-term memory/output bufferccount of their poor non-word reading cannot be excluded.he present study sought to address whether JH, who presenteds an acquired case of phonological dyslexia, had any of thedditional impairments expected under an account of phonolog-cal dyslexia in which a causally linked constellation of deficitso-occurs (as in the subtypes described above).

As a final issue, Howard and Nickels (2005) make the impor-ant point that there can be orthographic (spelling) influencesn some of the tasks assumed to tap “phonological manipu-ation/phonological skills”; indicating that good performancen such tasks may result from preserved orthographic ratherhan phonological processes. In line with this proposal, Castles,olmes, Neath, and Kinoshita (2003) examined the relationshipetween phoneme deletion and spelling “transparency” (i.e. theegree to which an item has a direct letter-sound spelling cor-espondence). They report that healthy adults found deletionasier (better accuracy and faster reaction times) with transpar-nt items (e.g. BUCKLE) relative to opaque items (KNUCKLE).pelling skill also correlated with accuracy on transparent andot opaque items. Of particular relevance is that they suggesthat a much better measure of ‘phonological skill’ would beo use opaque items (in order to rule out the use of an ortho-raphic spelling strategy). Thus any study of a phonologicalyslexic’s ‘phonological ability’ that claims that performancen tasks such as segmentation and blending are well preserved,ust also determine that this is due genuinely to phonological

ather than orthographic factors. The present work will thereforexamine this issue in greater detail.

. Case description

JH is a 62-year old, right-handed male who left full-time

ducation at 16, joining the RAF and subsequently working asart of its Intelligence department. At the time of testing he hadecently retired from a managerial post. JH’s medical historynvolves treatment for Lupus (which involves low thyroid func-

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ion). In December 2002, JH suffered a heart attack and wasdmitted to a local hospital. Subsequently, that evening, JH hadstroke and was eventually discharged 9 days later after hav-

ng made some recovery. Speech and language was affected asconsequence of the stroke and he received speech and lan-

uage therapy over several sessions in early 2003. At present,H’s speech is well formed and fluent, with some hesitations andord finding problems. He currently walks with a cane, as he has

ome limited mobility on his right side. A CT scan conducted inuly 2005 determined the presence of a mature left anterior cir-ulation infarct. At the same period, neurological examinationf JH was unremarkable and, apart from his mobility difficulty,here was no evidence of limb or speech apraxia. There was alsoo evidence of hearing loss or visual impairment.

Three initial clinical testing sessions (October–November003) were conducted by the authors, during which JH’s perfor-ance on a variety of verbal and non-verbal tasks was examined

see Table 1). Subsequent testing was conducted over the fol-

able 1asic neuropsychological data

Norms

ini-mental state—30/30 29aven’s progressive matrices—11/12 10CST—6/6 6

enton—21/27 20

ORBObject decision test—124/128 115Item match test—32/32 30Foreshortened match test—25/25 22

RMTFaces—39/50 42Words—30/50 43

luencySpoken initial letter (FAS)—10 36Spoken animals—5 17

rammatical/syntactic processingTROG—75/80 78

amingGNT—21/30 15

emanticsPPT—49/52 50PALPA 50: synonyms—52/60 56ADA: written word/pix matching—66/66 65

eadingNART—33/50 18PALPA 36: non-words-length—13/24

epetitionPALPA 9: words/non-words—78/80 79PALPA 7: syllable length—24/24Gathercole et al. (1994): non-word repetition—35/40 33N. Martin—minimal pairs; immediate: 32/32; filled delay: 32/32

ORB, Birmingham object recognition battery; NART, National Adult Readingest; PALPA, psycholinguistic assessments of language processing in aphasia;ROG, test for the reception of grammar; WCST, Wisconsin card sorting test;MS-III, Wechsler memory scale third edition; WRMT, Warrington’s recog-

ition test; PPT, Pyramids & Palm trees test; Benton, Benton facial recognitionest; ADA, action for dysphasic adults battery; GNT, graded naming test.

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owing 18 months (January 2004–June 2005), a period duringhich JH showed no changes in presentation. Despite impaired

peech production, JH demonstrates normal abilities on routineomestic day-to-day activities such as cooking, cleaning, shop-ing, driving, etc. He is a very keen bridge player, and is morehan capable of playing at a reasonable standard.

.1. Summary of initial testing results

JH’s overall cognitive profile was determined by thoroughesting of his ability on a variety of cognitive tasks (see Table 1).is performance on measures of general cognitive function,

xecutive function (all six categories were completed on theCST, for example), and object and face recognition was

ormal, demonstrating little generalised cognitive impairment.rammatical and syntactic processing (TROG), and measuresf reading, repetition and naming ability, also showed littlempairment. JH showed better recognition of non-verbal com-ared with verbal material (see WRMT) and some problemsith semantic processing, but this disruption was also very mild

see synonym judgement).As an additional means of determining the quality of JH’s

peech production, we asked him to provide an account of whats occurring in the “Cookie Theft” picture (May 2005): “Theink is overflowing but the the the er. the mummy is washing uplongside there and erm. and the boy is erm. erm. wanting toet cookie jar out but he’s er. he he he is er. climbing on top ofhe chair and the chair is tipping over and er. and in his hande’s got some cookies to give to his daughter.. his his his erm.aughter, no..she’s ah! [laughs] you could find erm.. and erm..pauses 5 s) I think that’s all.” (total time—61 s). It is apparentrom this example, and from the data in Table 1 indicating thatord fluency is somewhat poor, that JH has mild difficulties inynamic speech production (though given his relatively gooderformance on the Graded Naming Test, he is not classicallynomic). His speech is well formed, however, and there was novidence on any phonological output task of phonological errors.nitial screening also demonstrated that despite JH’s normal per-ormance on word reading (NART), he was severely impairedt reading a list of non-words (PALPA 36). For this reason weought to examine his word/non-word reading in greater detail toetermine whether his profile was consistent with phonologicalyslexia.

.2. Summary of reading testing results

Subsequent to the initial screening, further testing of JH’seading and spelling was undertaken (see Table 2). JH showed nompairment of recognising familiar words, discriminating lettersr naming letters. However, he was very impaired at ‘soundingut’ letters, and such impairment has been reported in severalther phonological dyslexic cases. Patterson and Marcel (1992)rgued that an impairment of ‘sounding out’ letters reflected an

nability to extract the appropriate sounds corresponding to let-ers by referring to previously learnt words (i.e. to sound outhe letter ‘C’ you would simply say the first phoneme in CAT).n effect, this proposal suggests that a task like ‘sounding out’

2866 J.J. Tree, J. Kay / Neuropsycholo

Table 2Test data relating to reading and spelling

Lexical decisionPALPA 25: visual—118/120

Letter processingPALPA 21: letter discrimination—60/60PALPA 22: letter naming—26/26PALPA 22: letter sounding—15/26

Reading—wordsWeekes (1997): frequency vs. length—198/200PALPA 30: syllable length—24/24PALPA 31: frequency vs. imageability—79/80PALPA 32: grammatical class—80/80PALPA 33: grammatical class—39/40PALPA 34: morphology—90/90PALPA 35: regularity—60/60

Reading—non-wordsWeekes (1997): length—session 1: 64/100; session 2: 66/100Palpa 36: length—14/24Howard and Best (1996): complexity—92/132

Short/simple: 38/45Long/simple: 29/44Long/complex: 25/43

Writing to dictationPALPA 39: letter length—23/24PALPA 40: imageability vs. frequency—73/80PALPA 44: regularity—33/40PALPA 41: grammatical class—16/20PALPA 43: morphology—24/30

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ALPA, psycholinguistic assessments of language processing in aphasia.

etters is analogous to a segmentation task and as such poorerformance is likely to reflect a generalised impairment of thehonological system (Patterson et al., 1996). However, later evi-ence will show that this proposal is unlikely given JH is veryble to segment and blend words. We would contend that it isore likely that JH’s impairment in providing sounds to letters

eflects specific disruption to letter sound correspondences (e.g.o ‘phoneme assignment’ in which grapheme–phoneme corre-pondence rules play a part; Coltheart et al., 1993).

.3. Reading aloud words and non-words

JH performed with ease all the tests of word reading,howing no effects of length, frequency, imageability or reg-larity (see Table 2). Reading aloud was swift and accu-ate. Of critical importance, JH showed no part of speechffects or difficulties with morphology. This clearly demon-trates that his profile is not consistent with an impairmentf ‘direct’ orthographic-phonological connections (i.e. subtypeof phonological dyslexia discussed earlier), as he shows no

vidence of poorer performance reading words with low seman-ic/conceptual content (i.e. poor function word reading or image-bility effects). In addition, we tested JH’s reading of words in

ext (using the “Grandfather passage”, taken from the Apraxiaattery for Adults, Dabul, 1979). Consistent with his single word

eading, JH performed flawlessly with a rapid rate of production51 s to read the entire passage).

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gia 44 (2006) 2861–2873

In stark contrast, JH’s performed consistently poorly wheneading lists of non-words. On an initial non-word list manip-lating length, JH showed poorer performance on longer rel-tive to shorter non-words (PALPA 36—3 letter, 6/6; 4 let-er, 4/6; 5 letter, 4/6; 6 letter, 0/6). In a subsequent non-ord test devised by Weekes (1997), JH again showed clear

ffects of letter length, observed consistently over two ses-ions a year apart (Session 1 (April 2004)—3L = 25/25,L = 10/25, 5L = 15/25, 6L = 14/25—Wald(1) = 6.88, p = 0.009;ession 2 (April 2005)—3L = 23/25, 4L = 16/25, 5L = 13/25,L = 14/25—Wald(1) = 7.97, p = 0.005). Weekes (1997) demon-trated an effect of letter length in non-word reading speed inealthy adults, and interpreted this effect as being consistent withhe serial nature of the non-lexical reading route. The presenttudy provides further evidence that impairment of this route canave a consequential impact of letter length on non-word readingccuracy. An additional test of non-word reading using stimulirovided by Howard and Best (1996), examined whether letterength or complexity had a greater impact on JH’s non-wordeading accuracy (longer strings may in fact be more complexrthographically). In this case an effect of letter length remainedWald(1) = 3.94, p = 0.05), and there was no effect of complexityWald(1) = 0.566, p = 0.46). This length effect will be consideredurther, below.

Overall, across the three non-word reading tests, JH scored36/356 (0.66) correct. This places his non-word reading impair-ent at the milder end of the continuum of reported cases.onetheless, other cases of phonological dyslexia have been

eported to perform in the same range (RR (0.63), Bisiacchi etl., 1989; WE (0.65), Berndt et al., 1996; BR (0.66), Friedman,996; AG (0.69), Caramazza, Miceli, Silveri, & Laudanna,985). Most importantly, JH performs at an equivalent levelo case WBA (0.77 accuracy) who was amongst five cases ofhonological dyslexia with additional generalised phonologi-al impairments reported by Patterson and Marcel (1992). JH’srrors on non-words were responses corresponding to real wordse.g. BORTH—“Broth”); a phenomenon referred to ‘lexicalisa-ion’ or as ‘lexical capture’ (Funnell & Davison, 1989), andypically reported in cases of phonological dyslexia. Across allhree non-word reading tasks, 60% (72/120) of error responsesere ‘lexicalisations’, a proportion in a similar range to that

een in other reported cases. Overall, then, JH’s performancen reading aloud non-words in terms of accuracy and error types comparable to that observed in other cases of phonologicalyslexia.

.4. Spelling words and non-words

JH’s spelling ability with familiar words was examined. Over-ll, he showed a mild impairment, compared with reading aloudhe same words, although there was no evidence of effects ofength or regularity. All errors JH made on a test manipulat-ng frequency versus imageability (PALPA 40) were with items

hat were both low frequency and low imageability. Importantly,here was no evidence of poorer spelling performance on func-ion words or particular difficulties with morphology. However,n contrast to his non-word reading, JH’s spelling of non-words

chologia 44 (2006) 2861–2873 2867

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Table 3Test data relating to phonological processing

Rhyme judgement—(auditory presentation)Hanley et al. (2004): words—16/16PALPA 15: words—52/60PALPA 15: words (no orthographically similar pairs)—29/30Best (unpublished): non-words—47/50Morrison (2001): words—143/144Morrison (2001): three word odd one out—23/24

Rhyme judgement—(written presentation)PALPA 15: words—40/60Best (unpublished): non-words—31/50Tree and Kay (unpublished)Words—38/40; non-words—36/40

Homophone judgementPALPA 28—53/60 (all errors on non-words)Coltheart—homophone test

Regular—47/50Irregular—46/50Non-words—37/50

Tree and Kay (unpublished)Words—38/40; non-words—35/40

SegmentationPALPA 16: initial sound—44/45PALPA 17: final sound—44/45Hanley et al. (2004): initial sound—16/16Hanley et al. (2004): final sound—16/16Patterson and Marcel (1992)

Initial sound (auditory): 45/48Initial sound (written): 31/48

Nickels (unpublished): final sound—45/46Morrison (2001)—three word odd one out: final sound—25/26Castles et al. (2003)

Initial sound (auditory): 26/30Final sound (auditory): 23/30

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J.J. Tree, J. Kay / Neuropsy

as substantially better. This clearly demonstrates that in thisase his poor performance with non-words was specific to read-ng (and that his non-word processing was not generally poor).H’s relatively well-preserved spelling performance thereforehows some dissociation between the phonological processesnderpinning reading and spelling.

.5. Phonological processing

Having determined that JH’s reading impairment was con-istent with phonological dyslexia, we examined his ability onvariety of phonological based tasks to determine the presencef any ‘generalised’ phonological impairment.

.6. Segmentation and blending

Previous studies of phonological dyslexia have claimed thathere is a link between poor non-word reading and impairmentsn measures of segmentation and blending (e.g. Patterson &arcel, 1992). Testing of JH’s segmentation ability involved

oth initial and final phoneme segmentation (i.e. “please sayAT without the first sound” versus “please say CAT without the

ast sound”). Several versions of this task were used. Across allests, JH performed well (see Table 3). It is especially noteworthyhat although these tests included both word/non-word stimuli,here was no evidence of a lexicality effect.

One auditory segmentation test (taken from the Phonologyesource Pack for Adults, Morrison, 2001) was included inhich JH had to identify the two out of three items that shared

he same final phonemes. Such a task was administered to deter-ine whether JH’s performance on segmentation tasks declined

s a function of processing load. However, as with all ear-ier testing, JH performed well. He also performed well onhe auditory version of the initial phoneme segmentation testevised by Patterson and Marcel (1992): JH: 45/48; Controls5/48. He was impaired, however, when these items (words andon-words) were presented in the written modality (JH: 31/48;ontrols: 45/48). JH’s performance on tasks of phonologicallending/assembly (e.g. AT plus K makes what?) was examined.n both cases JH performed well (Patterson & Marcel, 1992: JH5/48, Controls 43/48; Nickels—JH 42/46, Controls 42/46) andhere was no evidence of any lexicality effect.

We described earlier that Howard and Nickels (2005) haveuggested that orthographic (spelling) influences may maskood performance on segmentation and blending tasks, such thatood performance may involve particular orthographic strate-ies (i.e. good spelling ability), rather than phonological abilityer se. In order to determine if this underlay JH’s good per-ormance on earlier testing, we made use of a set of stimulitaken from Castles et al., 2003) that manipulates spelling ‘trans-arency’ (i.e. the degree to which an item has a direct letter-ound spelling correspondence). Overall, JH performed withinhe normal range (relative to the young controls tested by Castles

t al.) on this task: initial phoneme: JH 26/30, Controls 25/30;nal phoneme: JH 23/30, Controls 20/30. Of critical importance

s the finding that JH showed no greater impairment with opaqueelative to transparent items: initial phoneme errors: 3, transpar-

aips

Patterson and Marcel (1992): initial sound—45/48Nickels (unpublished): final sound—42/46

nt; 2, opaque; final phoneme errors: 3, transparent; 5, opaque,hich clearly demonstrates that JH’s good segmentation perfor-ance is not dependent on an orthographic strategy.

.7. Rhyme/homophone judgement

Two initial tests of word and non-word rhyme judgementere administered in auditory and written versions. While forritten items, JH performed very poorly (at 66% correct), heas also mildly impaired in making auditory rhyme judgements

85% correct), both for words and non-words (McNemar changeest indicated a significant difference between performance onuditory and written versions, χ2 = 7.21, d.f. = 1, p = 0.004). Forritten word rhyme judgement, error responses demonstrated a

trong tendency to accept visually similar non-rhyme items (i.e.aying ‘yes’ to the items, CHEAT-SWEAT; 17 false positiverrors, 12 visually similar items, 5 visually dissimilar items),

nd interestingly, a similar pattern of selecting visually sim-lar non-rhyme items was observed when the materials wereresented aurally (6/8 errors). This finding was curious givenubsequent testing of the PALPA 15 stimuli showed JH was

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ery capable of reading aloud all these items without prob-em.

As it was possible that JH was incorrectly choosing to base hisecision on visual ‘rhyme’, we re-administered this test aurallyithout the visual foils, and, in addition, tested his auditory per-

ormance on a large set of visually dissimilar rhyme/non-rhymetems (Morrison, 2001). In both cases, JH performed well (seeable 3). He was also able to detect pairs of aurally presentedhyming (e.g. CAR – STAR) and non-rhyming (e.g. CHAIR

TICK) items, using a set devised by Hanley, Masterson,pencer, and Evans ( 2004) when instructed to ignore visu-lly similar pairs that do not rhyme. Finally, he was also ableo perform well on an auditory segmentation test (Morrison,001) that required the identification of two out of three itemshat rhymed. Therefore, on the basis of these findings we wouldrgue that JH can perform normally at these tasks when aurallyresented.

We also re-explored JH’s ability at written rhyme judge-ent using an additional test constructed by ourselves. This

ests included 40 word and 40 non-word items (10 visuallyimilar rhymes, 10 visually similar non-rhymes, 10 visuallyissimilar rhymes and 10 visually dissimilar non-rhymes) ande tested these items on 15 older adults (50+). Testing indi-

ated that JH’s score of 38/40 on word rhyme judgement wasithin normal range (Controls—mean = 38.5, S.D. = 0.75, z-

core = −0.66, n.s.) but with non-words JH’s score of 36/40as below normal range (Controls—mean = 38.2, S.D. = 1.06,

-score = −2.07, p = 0.02). Thus, consistent with his phonolog-cal dyslexia, these results indicated that JH was only impairedt written word rhyme judgement with non-word items. Inummary, then, we would conclude that, although he initiallyemonstrated a degree of poor performance on rhyme judge-ent (particularly visual rhyme judgement), subsequent testing

which importantly includes age-matched norms) suggests thate can perform well on these tests provided they utilise words.

It is curious that our earlier testing showed that JH wasnclined to make false positive errors on orthographically simi-ar foils, and this clearly indicates that he utilises orthographicnformation when deciding rhyme status. Previous work hasemonstrated a similar effect in healthy adults in that it haseen shown that orthographic similarity/dissimilarity can haven impact both on visual (Johnston & McDermott, 1986; Polich,cCarthy, Wang, & Donchin, 1983) and auditory rhyme judge-ent (Seidenberg & Tanenhaus, 1979), such that reaction times

nd errors rates were lowest with orthographically similarhymes and highest for orthographically similar non-rhymes.he fact is that our earlier testing showed that this effect wasxaggerated in JH’s case, and this may indicate a particular ‘strat-gy’ on his part. However, subsequent testing would suggest thate is not dependent on utilising this strategy, and perhaps expe-ience on such tasks warranted his abandoning it.

JH’s ability to make written homophone judgements waslso examined (e.g. do SUN and SON sound the same?), with

oth words and non-words. Homophone judgement clearly dif-ers from written rhyme judgement in that no segmentationf the written form is needed. Rather, success requires com-arison of whole word phonological forms. Our initial test-

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gia 44 (2006) 2861–2873

ng indicated that JH showed good performance on this tasksee Table 3), with both regular and irregular words. Homo-hone detection accuracy was impaired only with non-wordtems, consistent with his poor non-word reading ability. Inine with our testing of visual word rhyme judgement, welso administered an additional test constructed by ourselves.s with the word rhyme judgement task this homophone task

ncluded 40 word/non-word items (10 visually similar homo-hones, 10 visually similar non-homophones, 10 visually homo-hones and 10 visually dissimilar homophones) and as beforee also tested these items on 15 older adults (50+). For homo-hone judgement with JH scored 38/40 with words which wasithin normal range (Controls—mean = 38.5, S.D. = 0.84, z-

core = −0.83, n.s.), but only 35/40 with non-words which wasmpaired (Controls—mean = 37.4, S.D. = 0.99, z-score = −2.42,= 0.01). Thus these data are again consistent with his phonolog-

cal dyslexic impairment, in that poor performance is contingentn the utilisation of non-word items. In sum, these data indicatehat JH has little general impairment in the extraction and manip-lation of phonology. In particular, our findings are consistentith a reading impairment specifically affecting non-words.

.8. Auditory verbal short-term memory (AVSTM)

We next sought to determine whether JH’s pattern of per-ormance is linked in some way to an underlying impairment ofVSTM. It is apparent that many cases of phonological dyslexiaresent with a concurrent impairment of AVSTM (Friedman,996), and as a result, several authors have attributed a role ofn impaired phonological ‘output’ buffer to their patients’ pooron-word reading (Caramazza, Capasso, & Miceli, 1996). Inhe case of the three Alzheimer’s disease cases (RG, MO andB) reported by Caccappolo-van Vliet et al. (2004a,b), all pre-ented de facto with impairments of auditory verbal short-termemory. The authors argue that if this impairment had a role

o play in the patients’ non-word reading, a length effect shoulde present. However, it is unclear how thoroughly effects ofength were explored in non-word reading, and the nature of thetimuli that were selected (e.g. whether factors such as visualomplexity were controlled). As a result, we must accept theonclusions of Caccappolo-van Vliet et al. (2004a,b) regardinghe potential role of AVSTM in their patients’ non-word readingith some caution, particularly as no other measures of outputuffer impairment were taken.

In the case of JH, our testing of AVSTM (see Table 4)emonstrated: (1) an auditory digit span of six (consistent withormal performance, see Lezak, 1995); (2) poorer span for visualelative to auditory presented items (a reverse pattern is typ-cally reported in cases of AVSTM impairment, see Vallar &addeley, 1984); (3) normal span performance on a spatial span

ask (suggesting no generalised span impairments). It shoulde noted, however, that backwards span (for both aural/visualresented items) is impaired, but, given the additional process-

ng demands implicated in performing this task, this is likely toeflect some disruption of working memory (Gathercole, 1997)hat is unlikely to have a substantial role in the reading of singleon-words.

J.J. Tree, J. Kay / Neuropsycholo

Table 4Test data relating to auditory verbal short-term memory function

Short term memoryDigit span—(auditory)

Forward: 6Backward: 3

Digit span—(visual)Forward: 4Backward: 2

Spatial spanForward: 5Backward: 4

Word span(Auditory)—four items(Visual)—two items

Rhyme span: (Martin et al., 1994)—6

Length effects—(four words)Auditory short: 0.77Auditory long: 0.62Visual short: 0.55Visual long: 0.30

Phonological similarity effect—(four words)Auditory phonological similar: 0.45Auditory phonological dissimilar: 0.83Visual phonological similar: 0.33Visual phonological dissimilar: 0.55

Non-word reading—phoneme length manipulatedThree phoneme items—9/30 (0.30)

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A final test devised by Martin, Shelton, and Yaffee (1994)as used to examine JH’s auditory rhyme span. In this task, a

equence of words is read out and after a pause a probe word isead and the participant must decide if the probe rhymes with anyf the items in the previously presented sequence. There were4 trials for each sequence length (three to seven items), withach serial position being probed equally often. In this task, spans considered the optimal length by which a participant gets ateast 75% of trials correct. Despite the clear difficulty of this task,H performed very well, achieving a span of six items, whichs within normal range. This excellent performance, requiring ahyme judgement after a substantial delay, is clearly inconsistentith a generalised phonological impairment.As a further examination of the status of JH’s AVSTM, we

dditionally examined whether he showed effects of length andhonological similarity on immediate serial recall of aurally andisually presented items. Typically, patients with impairmentsf AVSTM show no such effects (see Vallar & Papagno, 2002,or a review) and we therefore wished to see what would happenith JH.

.9. Length effects in immediate serial recall

Research on AVSTM has determined that accuracy is typi-

ally better for sequences containing phonemically short com-ared with long words (e.g. Baddeley, Thomson, & Buchanan,975; Baddeley, Lewis, & Vallar, 1984). This result has beenrgued to reflect the maintenance of phonological codes (e.g.

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gia 44 (2006) 2861–2873 2869

oward & Franklin, 1988), and typically a ‘phonological loop’s attributed to this maintenance process (e.g. Baddeley, 1966,004). As a result, we sought to determine whether a similarffect was present in JH’s serial recall. A set of 12 phonologi-ally short and 12 long items were selected (all items were takenrom a set constructed by Mueller, Seymour, Kieras, and Meyer2003) which constitute a set of stimuli that have been rigor-usly controlled for confounding variables such as complexity;ee Baddeley, 2004). A series of 10 trials (consisting of fourtems in each sequence, each individual item being presentedn equal number of times) were constructed for auditory pre-entation and visual presentation. Entire lists were presented toH (in four blocks—two sets of short words and two sets ofong words) in eight testing sessions (five auditory presenta-ion and three visual presentation sessions, spanning May–June005). Overall accuracy is presented in Table 4. It is apparenthat JH performed better with lists of short versus long items,oth when items were presented aurally (means—short: 3.1,ong: 2.5; t(18) = 2.65, p = 0.016) and visually (means—short:.2, long: 1.2; t(10) = 6.50, p = <0.0001). These data provideurther evidence of normal AVSTM function in JH’s case, sug-esting that he is able to use a ‘phonological loop’ to supportequences of short relative to long words. This is a pattern that isever reported in cases of impaired AVSTM (Vallar & Papagno,002).

.10. Phonological similarity effects in immediate serialecall

Both auditory and visual immediate serial recall perfor-ance is modulated by the degree to which list items are

honologically similar (e.g. Baddeley, 1966, 1968; Levy, 1971;uce, Feustel, & Pisoni, 1983). In patients with impairmentsf AVSTM, it is typically reported that phonological similar-ty effects can be present for aurally presented stimuli, butot for visually presented items (Vallar & Papagno, 2002). Asfurther means of determining whether AVSTM impairmentas present, we examined whether JH showed differences in

ecalling phonologically similar/dissimilar lists. A set of 12honologically similar (e.g. cat, gap, cap, rat) and 12 phono-ogically dissimilar items were selected (e.g. wig, pen, car, jug,ot). A series of 10 trials of each (with four items in eachequence, each individual item being presented an equal numberf times) were constructed for auditory and visual presenta-ion. Entire lists were presented to JH (in four blocks—twohonologically similar (PS) and two phonologically dissimilarPDS)) in two separate testing sessions (run in parallel withhe length immediate serial recall testing in May–June 2005),ith the order of visual versus aural presentation counterbal-

nced. Overall accuracy is presented in Table 4. It is clear thatphonological similarity effect was present with both auditory

mean: PDS: 3.3/4, PS: 1.8/4; t(6) = 5.89, p = 0.001) and visu-lly presented items (mean: PDS: 2.2/4, PS: 1.3/4; t(6) = 4.14,

= 0.006). Overall accuracy was also poorer for the visually pre-

ented items (consistent with our earlier testing of span acrossodalities). As a final examination of AVSTM performance in

H, we collapsed his performance across all ISR testing and

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lotted a serial position curve, this demonstrated the typicallybow shaped’ function, with better accuracy at both the firstnd last serial position points, showing normal primacy andecency effects in his case (average auditory accuracy = 0.66;os 1 = 0.74, Pos 2 = 0.52, Pos 3 = 0.57, Pos 4 = 0.82; averageisual accuracy = 0.43; Pos 1 = 0.56, Pos 2 = 0.32, Pos 3 = 0.26,os 4 = 0.60).

.11. Phonological “output” buffer function

We reported earlier that JH showed a letter length effect inon-word reading. Such an effect could be considered to reflectn ‘output’ buffer impairment, as items with more letters willypically have more phonemes (although our earlier testing ofis homophone judgement performance and AVSTM do not sup-ort this account). Nonetheless, to test the possibility that JH’son-word reading impairment was related to an output buffermpairment, we examined his performance with a set of non-ords that manipulated phoneme length, while keeping letter

ength constant. In this test, the non-word items varied fromhree to five phonemes, but all were five letters long. None ofhe items had orthographic neighbours (all items were takenrom the online ARC Non-word Database, Rastle, Harrington,

Coltheart, 2002). JH’s non-word reading performance is pre-ented in Table 4. Although overall accuracy was poor (24/90orrect), there was no evidence of greater accuracy with threehoneme relative to five phoneme items. This finding clearlyemonstrates that JH’s non-word reading impairment is unlikelyo be due to an ‘output’ buffer impairment. Overall, our testingf JH’s AVSTM function showed: (1) superior auditory versusisual span; (2) the presence of length effects for auditory pre-ented items; (3) the presence of phonological similarity effectsor both auditory and visually presented items; (4) no effect ofhoneme length on non-word reading accuracy. These findingsould suggest that JH’s has no impairments to the functional

omponents of an AVSTM system (i.e. a normal phonologicalnput/output and rehearsal system) and by extension rules out theossibility that such impairment (particularly an output buffermpairment) may in some way underpin his poor non-word read-ng performance.

. General discussion

In the Introduction to this paper, we discussed the two ‘sub-ypes’ of phonological dyslexia outlined by Friedman (1995) aseing consistent with a ‘triangle’ model account of this disorderi.e. a model with no non-lexical reading route): (1) a generalisedisruption of phonological processing; reflected by impairmentsf phonological manipulation (i.e. segmentation/blending tasks)nd/or impairment on measures of phonologically based short-erm memory (i.e. span and rhyme judgement tasks); (2) anmpairment of the O → P reading pathway (see pathway B inig. 2); reflected by a deficit in function word reading. Only the

econd of these accounts can be construed as an impairment thats reading-specific, and earlier we pointed out that this accountemains problematic for the most recently implemented versionsf the ‘triangle’ model.

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gia 44 (2006) 2861–2873

Our subsequent testing of JH did not find impairments ineading function words suggesting that it is unlikely that hiseading performance is consistent with (2). He also showed nompairments in segmentation, blending, rhyme and homophonyasks, and normal functioning of phonological based short-term

emory (i.e. normal auditory digit span, length/phonologicalimilarity effects, no phonemic length effects in non-word read-ng), inconsistent with (1). As a result, this study provides thelearest evidence thus far that the non-word reading impair-ent in phonological dyslexia is reading specific. The fact that

H’s reading impairment is specific to non-words (and wordeading, especially of functors, is well preserved) is consistentith an explanation in terms of a disrupted non-lexical route

labelled A in Fig. 1). Thus although JH’s good reading of func-ors is potentially problematic for a ‘triangle’ model accountf his impairment, it is entirely consistent with the proposalsf the DRC model (Coltheart et al., 2001). In this model givenunctors are largely considered to be low in semantic quality,ormal performance with such items is considered to indicatereserved processing of a direct lexical (non-semantic) readingoute (marked B(ii) in Fig. 1) also known as the ‘third’ readingoute (see Coslett, 1991; Wu, Martin, & Damian, 2002). Hencet is apparent that not only is JH’s normal reading of functorsonsistent with a DRC account, but it is in fact predicted byuch an account given that the mechanisms involved in accurateesponding to such items are independent from those involvedn reading non-words.

.1. JH and other critical cases of phonological dyslexia

While it is apparent that the proposal that JH has a reading-pecific difficulty contrasts with the notion that there is a causalink between phonological impairment and poor non-word read-ng (the phonological impairment hypothesis of phonologicalyslexia; Patterson & Marcel, 1992), it is consistent with theeports of other cases of phonological dyslexia who performell on tasks of phonological processing (e.g. LB, Derouesne &eauvois, 1985; RG, MO and IB, Caccappolo-van Vliet et al.,004a,b). It is interesting to note that these cases differ from JHn terms of aetiology: LB had a right hemisphere CVA, and RG,

O and IB all had Alzheimer’s disease. JH provides evidencehat a similar behavioural profile can occur in conjunction withleft hemisphere focal lesion, and thus rules out the possibility

hat such performance only occurs in patients who are in someanner neurologically unrepresentative of the typical phonolog-

cal dyslexia patients reported in the literature (Coltheart, 1996).t is also important to emphasise that JH’s pattern of performances different from those other reported case studies in that, (a)B had some impairment in reading words (in particular, func-

ion words) and (b) RG, MO and IB were not tested sufficientlyo rule out the possibility that an ‘output’ buffer impairment

ay have underpinned their poor non-word reading. As a result,ll of these cases could be argued to have non-word reading

mpairments that are consistent with one of the subtypes setut above. We would suggest that the present study is thereforenique, given the thoroughness of phonological based testing inur particular case (including, for example, testing orthographic

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J.J. Tree, J. Kay / Neuropsy

transparency’ to exclude the use of orthographic strategies inhonological segmentation and blending tasks).

It is of note that although for the most part studies of phono-ogical dyslexia have typically omitted to examine in any detailhe role of a disruption to phonological short-term memory,ase ML (Lesch & Martin, 1998; Martin & He, 2004; Martin

Lesch, 1996) has been examined in a manner by which wean draw comparisons with JH. Case ML is reported to havereduced short-term memory in conjunction with phonologi-

al dyslexia. In a series of experiments, Martin and co-workersemonstrated that ML like JH performed at a similar level oneasures of immediate serial recall (average span = 2.3 items

or word lists), had a superior auditory versus visual span andemonstrated a phonological similarity effect with aurally pre-ented items. As a result, Martin and Lesch (1996) argued thatespite ML’s reduced span, his capacity to retain phonologicalnformation was intact. However, despite the fact that ML haseatures in common with JH, these cases differ on a numberf important dimensions: (1) ML appeared to have problemseading function words (see Martin & Lesch, 1996), (2) MLhowed no phonological similarity effect with written input, and3) ML’s span on the rhyme probe task constructed by Martin ando-workers was only three (see Martin & He, 2004). Whereas,H’s span on the same task was six and it is of note that ononsideration of published norms (Martin & He, 2004) his per-ormance was within normal range (5–10) and (4) JH showedlength effect with both aurally and visually presented items aattern that is never reported in patients with impaired phono-ogical short-term memory (see Vallar & Papagno, 2002). Asresult, we would argue that although both JH and ML share

eatures in common, JH constitutes a ‘cleaner’ example of aase that refutes the potential accounts provided by the ‘trian-le’ model.

As a final point, we note that evidence of a letter lengthffect was consistently observed in JH’s non-word reading accu-acy (but not in word reading). Which begs the question, ishe presence of a length effect contingent on lexical status anding that is consistent with an impairment of a non-lexicaleading mechanism? Using his dual-route cascaded model, Colt-eart (personal communication) provides evidence that supportsuch a possibility via manipulation of the parameter (knowns the grapheme–phoneme-correspondence interletter interval)hat dictates processing of the non-lexical route. For example,sing the set provided by Weekes (1997), when this parameteras set at its default value (13 cycles), the model accurately

ead all word and non-word items. However, when this param-ter was increased (20 cycles); (1) word accuracy remained00%, but non-word accuracy dropped to 83%, (2) errors onon-words increased as a function of length (3 letters = 100%, 4etters = 92%, 5 letters = 84%, 6 letters = 56%) and (3) a high pro-ortion of these errors were lexicalisations (12/17).2 These data

re therefore a good illustration of the fact that the kind of lengthffects seen in JH are at least in principle consistent with the pre-ictions indicated by disruption of the serial non-lexical reading

2 We are very grateful to Prof. Max Coltheart for these illustrative data.

tarl

gia 44 (2006) 2861–2873 2871

echanism in the dual-route cascaded model (Coltheart et al.,001). The main point is that under the principles of the DRCodel, length effects in word reading are by definition impli-

ated by the non-lexical reading route. Hence, any disruptiono the non-lexical mechanism will clearly result in a reductionf a length effect seen with words. The same would not be truef non-words, since they remain entirely dependent on the non-exical reading route.3 It is also noteworthy that this is not thenly way a pattern of phonological dyslexia can potentially beimulated within this model, other manipulations include, (a)elaying the onset of operation of the non-lexical route or (b)educing the strength of activation of activation of the phonemeevel. As a result, we intend to undertake further work, usingehavioural testing and simulation studies, to explore the naturef JH’s non-word reading impairment with reference to the DRCodel. This aspect has been somewhat neglected in investiga-

ions of phonological dyslexia (i.e. whether length effects arebsent or present in non-word reading has not generally beenested).

.2. Falsification of theories on the basis of single cases:he search for the ‘black swan’

One particular pursuit of Cognitive Neuropsychology haseen the identification of cases with profiles that contradict thoseredicted by current theories; the detection of a so-called ‘blackwan’ (referring to the axiom that “all swans are white” cane robustly falsified once one sees a single non-white swan).onetheless, the identification of such cases is for the mostart a considerable challenge, given individual variability in pre-orbid performance, and the diffuse nature of the brain damage,ith variable functional impairment as a consequence. Despite

hese challenges, we have argued that our findings do not fithe claim of a causal link between phonological impairment andoor non-word reading (the phonological impairment hypoth-sis) in phonological dyslexia and that JH is indeed a ‘blackwan’.

One criticism of the data may be that JH’s phonologicalyslexia can be considered to be ‘mild’ (although as we haveointed out, his profile, both in terms of level of accuracy andype of non-word error is not out of line with some other casesf phonological dyslexia). Could it be that JH’s poor non-wordeading is therefore a result of a phonological impairment thats so mild as to be undetectable on our tests? We have carriedut a variety of segmentation, blending, rhyme and homophonyasks using materials that were at least as complex as thosesed in non-word reading, yet nonetheless we could find novidence for a phonological impairment that might account for

3 The reverse would be true in the event of word reading being dependent onhe non-lexical reading route (as seen in surface dyslexia). In this case the DRCccount would predict an increase in length effects for regular word readingelative to controls, such a pattern of performance has been reported in theiterature (see Gold et al., 2005).

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on-word reading ability is commensurate with that of JH. Weontend that the challenge for those supporters of the phono-ogical impairment hypothesis is to clarify whether there areurther tests that might be used with JH, and cases like him,therwise the phonological impairment hypothesis becomesffectively unfalsifiable. The fact remains that JH is impairedt non-word reading, and therefore some kind of functionalccount must explain why he is poor at this task, but otherwise soood at a variety of other tasks that involve novel phonologicalodes. At present, no theoretical model provides a sufficientlyne-grained account of the relationship between degree of gen-ralised phonological impairment (on the basis of measuresike segmentation/blending) and consequential non-word read-ng impairment. This study demonstrates the importance of suchchallenge for future models of reading and phonology.4

cknowledgements

We are most grateful to both JH and his wife for consentingo participant in this research, it was a pleasure and privilege toork with them both. We would like to thank Max Coltheart,athy Rastle and two anonymous reviewers for their helpful

dvice and comments relating to a previous version of thisanuscript. We would also like to thank Wendy Best, Jess Craib,ick Hanley, David Howard, Nadine Martin, Randi Martin, Lyn-sey Nickels, Jo Walford and Brendan Weekes for providing thetimulus materials and data relating to various tests utilised withH.

eferences

addeley, A. D. (1966). Short-term memory for word sequences as a functionof acoustic, semantic, and formal similarity? Quarterly Journal of Experi-mental Psychology, 18, 362–365.

addeley, A. D. (1968). How does acoustic similarity influence short-term mem-ory? Quarterly Journal of Experimental Psychology, 20, 249–264.

addeley, A. D. (2004). Working memory: Looking back and looking forward.Nature Reviews: Neuroscience, 4, 829–839.

addeley, A. D., Lewis, V. J., & Vallar, G. (1984). Exploring the articulatoryloop. Quarterly Journal of Experimental Psychology, 36, 233–252.

addeley, A. D., Thomson, N., & Buchanan, M. (1975). Word length and thestructure of short-term memory. Journal of Verbal Learning and VerbalBehaviour, 14, 575–589.

erndt, R. S., Haendiges, A. N., Mitchum, C. C., & Wayland, S. C. (1996).An investigation of non-lexical reading. Cognitive Neuropsychology, 13,763–801.

isiacchi, P. S., Cipolotti, L., & Denes, G. (1989). Impairment in processingmeaningless verbal material in several modalities: The relationship betweenshort-term memory and phonological skills. Quarterly Journal of Experi-

mental Psychology, 41A, 293–319.

accappolo-van Vliet, E., Miozzo, M., & Stern, Y. (2004a). Phonologicaldyslexia without phonological impairment? Cognitive Neuropsychology, 21,820–839.

4 It is noteworthy that the proposal of a theoretical model that posits a rela-ionship between degree of impairment on segmentation, blending and non-wordeading may already seem unlikely on the basis of the current facts. For example,eturning to the original study by Patterson and Marcel (1992), on the basis ofhe case series they present, it is apparent that no such relation appears to existe.g. WBA their least impaired non-word reader was severely impaired on theiregmentation and blending tasks).

H

H

H

H

H

gia 44 (2006) 2861–2873

accappolo-van Vliet, E., Miozzo, M., & Stern, Y. (2004b). Phonologi-cal dyslexia: A test case for reading models. Psychological Science, 15,583–590.

aramazza, A., Capasso, R., & Miceli, G. (1996). The role of the graphemicbuffer in reading. Cognitive Neuropsychology, 13(5), 673–698.

aramazza, A., Miceli, G., Silveri, M. C., & Laudanna, A. (1985). Readingmechanisms and the organization of the lexicon: Evidence from acquireddyslexia. Cognitive Neuropsychology, 2, 81–114.

astles, A., Holmes, V. M., Neath, J., & Kinoshita, S. (2003). How does ortho-graphic knowledge influence performance on phonological awareness tasks?Quarterly Journal of Experimental Psychology, 56A(3), 445–467.

oltheart, M. (1996). Phonological dyslexia: Past and future issues. CognitiveNeuropsychology, 13(6), 749–762.

oltheart, M., Curtis, B., Atkins, P., & Haller, M. (1993). Models of readingaloud: Dual-route and parallel-distributed-processing approaches. Psycho-logical Review, 100, 589–608.

oltheart, M., Rastle, K., Perry, C., Langdon, R., & Ziegler, J. (2001). A dualroute cascaded model of visual word recognition and reading aloud. Psy-chological Review, 108, 204–256.

oslett, H. B. (1991). Read but not write idea—Evidence for a third readingmechanism. Brain and Language, 40, 425–443.

erouesne, J., & Beauvois, M. F. (1979). Phonological processing in reading:Data from alexia. , Journal of Neurology, Neurosurgery and Psychiatry, 42,1125–1132.

erouesne, J., & Beauvois, M. F. (1985). The “phonemic” stage in the non-lexical reading process: Evidence from a case of phonological alexia. In K.E. Patterson, J. C. Marshall, & M. Coltheart (Eds.), Surface dyslexia: Neu-ropsychological and cognitive studies of phonological reading. Hillsdale,NJ: Erlbaum.

arah, M., Stowe, R. M., & Levinson, K. L. (1996). Phonological dyslexia:Loss of a reading-specific component of cognitive architecture? CognitiveNeuropsychology, 13, 849–868.

riedman, R. B. (1995). Two types of phonological alexia. Cortex, 31, 397–403.riedman, R. B. (1996). Phonological text alexia: Poor pseudoword reading plus

difficulty reading functors and affixes in text. Cognitive Neuropsychology,13, 869–885.

unnell, E. (1983). Phonological processes in reading: New evidence fromacquired dyslexia. British Journal of Psychology, 74, 159–180.

unnell, E., & Davison, M. (1989). Lexical capture: A developmental disorder ofreading and spelling. Quarterly Journal of Experimental Psychology, 41A,471–487.

athercole, S. E. (1997). Models of verbal short-term memory. In M. A. Conway(Ed.), Cognitive models of memory. Cambridge, MA: MIT Press.

old, B. T., Balota, D. A., Cortese, M. J., Sergent-Marshall, S. D., Snyder, A. Z.,Salat, D. H., et al. (2005). Differing neuropsychological and neuroanatom-ical correlates of abnormal reading in early-stage semantic dementia anddementia of the Alzheimer type. Neuropsychologia, 43, 833–846.

anley, J. R., Masterson, J., Spencer, L., & Evans, D. (2004). How long do theadvantages of learning to read a transparent orthography last? An investi-gation of the reading skills and incidence of dyslexia in Welsh children at10-years of age. The Quarterly Journal of Experimental Psychology, 57,1393–1410.

arm, M. W., & Seidenberg, M. S. (1999). Phonology, reading acquisition, anddyslexia: Insights from connectionist models. Psychological Review, 106,491–528.

arm, M. W., & Seidenberg, M. S. (2001). Are there orthographic impairmentsin phonological dyslexia? Cognitive Neuropsychology, 18, 71–92.

arm, M. W., & Seidenberg, M. S. (2004). Computing the meaning of wordsin reading: Cooperative division of labor between visual and phonologicalprocesses. Psychological Review, 111, 662–672.

inton, G., & Shallice, T. (1991). Lesioning an attractor network: Investigationsof acquired dyslexia. Psychological Review, 98, 74–95.

oward, D., & Best, W. M. (1996). Developmental phonological dyslexia: Real

word reading can be completely normal. Cognitive Neuropsychology, 13,887–934.

oward, D., & Franklin, S. (1988). Missing the meaning? A cognitive neuropsy-chological study of the processing of words in an aphasic patient. Cambridge,MA: MIT Press.

cholo

H

J

L

L

L

L

M

M

M

M

M

P

P

P

P

P

P

P

R

S

S

V

V

J.J. Tree, J. Kay / Neuropsy

oward, D., & Nickels, L. (2005). Separating input and output phonology:Semantic, phonological, and orthographic effects in short-term memoryimpairment. Cognitive Neuropsychology, 22(1), 42–77.

ohnston, R. S., & McDermott, E. A. (1986). Suppression effects in rhyme judge-ment tasks. Quarterly Journal of Experimental Psychology, 38A, 111–124.

esch, M. F., & Martin, R. C. (1998). The representation of sublexicalorthographic–phonologic correspondences: Evidence from phonologicaldyslexia. Quarterly Journal of Experimental Psychology, 51A, 905–938.

evy, B. A. (1971). The role of articulation in auditory and visual short-termmemory. Journal of Verbal Learning and Verbal Behaviour, 10, 123–132.

ezak, M. D. (1995). Neuropsychological Assessment (3rd ed.). New York:Oxford University Press.

uce, P. A., Feustel, T. C., & Pisoni, D. B. (1983). Capacity demands in short-term memory for synthetic and natural speech. Human Factors, 25, 17–32.

artin, R. C., & He, T. (2004). Semantic short-term memory and its role insentence processing: A replication. Brain and Language, 89, 76–82.

artin, N., & Lesch, M. F. (1996). Associations and dissociations betweenlanguage impairment and list recall: Implications for models of STM. In S.Gathercole (Ed.), Models of short-term memory. Hove: Lawrence ErlbaumAssociates Ltd.

artin, R. C., Shelton, J. R., & Yaffee, L. S. (1994). Language processing andworking memory: Neuropsychological evidence for separate phonologicaland semantic capacities. Journal of Memory and Language, 33, 83–111.

orrison, S. (2001). Phonology resource pack for adult aphasia. Oxford, UK:Speechmark Ltd.

ueller, S. T., Seymour, T. L., Kieras, D. E., & Meyer, D. E. (2003).Theoretical implications of articulatory duration, phonological similar-ity and phonological complexity in verbal working memory. Journal ofExperimental Psychology: Learning Memory and Cognition, 29(6), 1353–1380.

atterson, K. (1982). The relation between reading and phonological coding:

Further neuropsychological observations. In A. W. Ellis (Ed.), Normalityand pathology in cognitive functioning. London: Academic Press.

atterson, K., & Marcel, A. (1992). Phonological ALEXIA or PHONOLOGI-CAL alexia. In J. Alegria, D. Holender, J. J. de Morais, & M. Radeau (Eds.),Analytic approaches to human cognition. Amsterdam: North Holland.

W

W

gia 44 (2006) 2861–2873 2873

atterson, K. E., Seidenberg, M. S., & McClelland, J. L. (1989). Connectionsand disconnections: Acquired dyslexia in a computational model of read-ing processes. In R. G. M. Morris (Ed.), Parallel distributed processing:Implications for psychology and neuroscience. London: Oxford UniversityPress.

atterson, K. E., Suzuki, T., & Wydell, T. N. (1996). Interpreting a case ofJapanese phonological alexia: The key is in phonology. Cognitive Neuropsy-chology, 13, 803–822.

laut, D. C., & Shallice, T. (1993). Deep dyslexia: A case study of connectionistneuropsychology. Cognitive Neuropsychology, 10, 377–500.

laut, D. C., McClelland, J. L., Seidenberg, M. S., & Patterson, K. (1996).Understanding normal and impaired word reading: Computational principlesin quasi-regular domains. Psychological Review, 103, 56–115.

olich, J., McCarthy, G., Wang, W. S., & Donchin, E. (1983). When wordscollide: Orthographic and phonological interference during word processing.Biological Psychology, 16, 155–180.

astle, K., Harrington, J., & Coltheart, M. (2002). 358,534 non-words: The ARCnon-word database. Quarterly Journal of Experimental Psychology, 55A(4),1339–1362.

artori, G., Barry, C., & Job, R. (1984). Phonological dyslexia: A review. In R.N. Malatesha & H. A. Whitaker (Eds.), Dyslexia: A global issue. The Hague:Martinus Nijhoff Publishers.

eidenberg, M. S., & Tanenhaus, M. K. (1979). Orthographic effects on rhymemonitoring. Journal of Experimental Psychology: Human Learning andMemory, 5, 546–554.

allar, G., & Baddeley, A. D. (1984). Phonological short-term store, phono-logical processing and sentence comprehension: A neuropsychological casestudy. Cognitive Neuropsychology, 1, 121–141.

allar, G., & Papagno, C. (2002). Neuropsychological impairments of short-term memory. In A. D. Baddeley, M. D. Kopelman, & B. A. Wilson (Eds.),The handbook of memory disorders. Sussex, UK: Wiley.

eekes, B. S. (1997). Differential effects of number of letters on words andnon-word naming latencies. Quarterly Journal of Experimental Psychology,50A(2), 439–456.

u, D. H., Martin, R. C., & Damian, M. F. (2002). A third route for reading?Implications from a case of phonological dyslexia. Neurocase, 8, 274–295.