Developmental surface dyslexias - Naama Friedmann

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cortex 44 (2008) 1146–1160 1149 grapheme-to-phoneme conversion, although some conversions might be favorable. Even 3-letter words might theoretically have several thousands of possible readings. For example, in the word , QBS, each of the three letters can be converted to either of two consonants, and the vowels are not represented, so after each consonant letter one of six vowels can be used. Together with the two possible stress positions, this leads to 2 2 2 6 6 6 2 ¼ 3456 theoretical ways to read this word, which the orthographic lexicon narrows down to three lexical options. Another result of this structure of Hebrew orthography that is important for the description of surface dyslexia is the abundance of potentiophones (Gvion and Friedmann, 2001; Lukov and Friedmann, 2006). We use the term potentiophones for word pairs that are written differently and sound differently, but whose letter sequence can be mapped onto the same sound string. Therefore when such a word is read solely via grapheme-to-phoneme conversion, it can be read aloud as the other existing word, which sounds differently. An example in English is the word now that can be read as no or know when read via grapheme-to-phoneme conversion (other examples for English potentiophones are resent–recent, come–comb, bear– beer, angle–angel, talk–talc, and whose–hose). Examples for potentiophones in Hebrew are the pairs (KtR–QTR, /katar/–/keter/, locomotive–crown), (QMO–KMO, /kmo/–/ kamu/, like–woke up), and (XOL–XBL, /xol/–/xevel/, sand– rope). Potentiophones are valuable for the diagnosis of surface dyslexia, because reading aloud of these words can already indicate whether or not the reader used her lexical route for reading. They are better for the detection of surface dyslexia than homophones, because homophones sound the same and thus reading aloud cannot indicate whether they were read correctly or not, and they thus require comprehension tasks. Furthermore, potentiophones might be more sensitive to surface dyslexia reading than other irregular words because the reading of irregular words that do not have potentiophones results in a nonlexical response. Because some individuals with surface dyslexia have a strong tendency to produce real words as output (Patterson et al., 1985, p. 12), this nonlexical response may be identified by the reader as incorrect, and corrected immediately in an attempt to reach a lexical response. An incorrect reading of a potentiophone, however, yields an existing word, and hence does not allow the detection of the error. In the current study we used these characteristics of Hebrew orthography to examine surface dyslexia, and more specifically three subtypes of developmental surface dyslexia. We also explored the way surface dyslexia is manifested in a highly irregular language like Hebrew. 2. Experimental investigation 2.1. Participants 2.1.1. Participants with developmental surface dyslexia The participants with surface dyslexia were individuals who had developmental dyslexia, who were diagnosed with ‘‘learning disabilities’’ or ‘‘reading disabilities’’ prior to the study. We included them in the study based on the number and types of errors they made in single word reading. Participants were included in the study only if their reading aloud (see Section 2.2.1) included significantly more errors than the control group, and the type of errors they made in reading were errors that result from reading via graphemeto-phoneme conversion: regularizations, errors in vowel pattern of unvoweled words or words with ambiguous vowel letters, and potentiophone errors. The comparison of each participant to her/his control group was done using the Crawford and Howell’s (1998) t-test for the comparison of a single participant to a group. This created a group of 17 participants, six female and 11 male. Their background information is presented in Table 1. All the participants with developmental surface dyslexia had normal IQ, and studied in regular schools and regular classes. They had normal language, their spontaneous speech was normal and none of them was diagnosed with SLI (specific language impairment). Four of the participants (TM, OM, BZ, and YD) were tested with spoken language test batteries for the diagnosis of syntactic impairments (BAMBI, Friedmann and Novogrodsky, 2002; BAFLA, Friedmann, 1998), and a test battery for the assessment of phonological abilities (BLIP, Friedmann, 2003), showing performance within the norm in syntax and phonology. In order to avoid surface dyslexia-like reading that resulted from lack of sufficient exposure to reading, we only included participants who were in fifth grade and higher, and who had effective classroom instruction. Eleven of the participants were in fifth or sixth grade, four were in middle school, and two were adults. All of them had Hebrew as their mother tongue, and one was bilingual and had both Hebrew and English as mother tongues. They had no hearing impairment, and none of them had a history of neurological disease or head trauma that might have led to acquired Table 1 – Background information on the participants with developmental surface dyslexia Participant Age Grade Gender Handedness Remedial teaching SH 10;8 5 M R Yes GL 10;10 5 F R – OF 11;2 5 M R – YR 11;0 5 M R Yes TM 12;0 6 F R Yes NT 12;8 6 M R Yes OM 14;10 8 M R Yes BZ 43 Adult M R – AS 11 5 M R Yes OS 11 5 F R – AK 13;9 8 M R Yes AM 10;7 5 F R – AL 11 5 M R Yes KR 11 5 F R – NF 14;5 8 M R Yes IR 15;10 9 M L Yes YD 21 Adult F R Yes
1150 cortex 44 (2008) 1146–1160 dyslexia. As can be seen in Table 1, some of the participants received remedial teaching within or outside school. 2.1.2. Control groups A total of 68 individuals without reading or language impairment participated as control participants. They were tested with the same tests in order to assess the normal level of performance in each test. Because the participants with surface dyslexia were of three age groups, fifth to sixth grade, middle school, and adults, we administered the tests to three groups of individuals without reading or language impairments to attain reference scores for each age: 28 individuals in fifth grade, 24 individuals in middle school (seventh–ninth grade), and 16 adults aged over 21. 2.2. Methods 2.2.1. Reading aloud The route the participants used for reading aloud was assessed using a task of reading aloud of single words. The list included 340 Hebrew words, 220 irregular words with irregularity of an ambiguous consonant or silent letters, 140 of them without a potentiophone and 80 with potentiophones, and 80 relatively regular potentiophones. Words were defined ‘‘relatively regular’’ when they did not include irregularity of ambiguous letters, silent vowel letters, or vowel letters with irregular sound. We called them relatively regular rather than regular because they were still, like all Hebrew words, underspecified for vowels and stress. Sixteen of the relatively regular words without potentiophones included the regular (more frequent) conversion of vowel letters, and a sound for underrepresented vowels, which is usually the preferred conversion. The list also included 40 relatively regular words without potentiophones, which were compared to the irregular and potentiophonic words. In addition, in order to assess their ability to read via the sublexical route, five of the participants (who were still accessible for additional testing) read a list of 30 pronounceable nonwords (from TILTAN screening test, Friedmann and Gvion, 2003). Twenty of these nonwords were presented with diacritic points indicating the voweling, and 10 were unpointed (in the unvoweled nonwords, when no vowel letter was present, each vowel the participant chose was accepted as correct). A third of the nonwords was created by substitution of a single letter in existing words, a third by addition or substitution of the leftmost letter in an existing word, and another third was created by transposition of middle letters of an existing word. 2.2.2. Lexical decision In order to test whether the participants could use the orthographic input lexicon even if they read the words aloud via the sublexical route, we used a lexical selection task. The task included 75 pairs of letter sequences. Each pair included a word spelled correctly, and its pseudohomophone (knife– nife for a relevant example in English). The participants were asked to circle the existing word (the correctly spelled word) in each pair. 3 The target words included irregular words (chef–shef, key–kee), and words with a homophonic letter (cinema–sinema). (Because more than half of the letters in Hebrew, 13 of the 22 letters, can be mapped onto the same sound as another letter, most of the words have a pseudohomophone, and most of the words need orthographic–lexical information for correct selection. See Appendix A.) 2.2.3. Semantics For the assessment of the comprehension of homophones and potentiophones we used a task with triads of written words. The task included 40 triads, each triad including a target word and two words – one word was associated semantically with the target word, the other word was a homophone or potentiophone of the associated word. The participants had to choose the word that was semantically associated with the target word. For example, for the target word lettuce, we gave the words cabbage and near, which are potentiophones in Hebrew ( ; /kruv/–/karov/), and the participant had to choose cabbage, which was semantically related to the target word lettuce. (A possible example for English would be asking the participant to choose between the potentiophones bear and beer for the target word drink.) 2.2.4. Naming To examine the status of the phonological output lexicon of our participants, we also included a task of naming 100 color pictures of objects (SHEMESH, Biran and Friedmann, 2004, 2005, 2006; Friedmann and Biran, 2003). The participants were presented with a picture and were asked to name it aloud. We collected the responses, including hesitations and self-corrections. Hesitations longer than 5 sec and incorrect first responses were counted as incorrect responses. This task was administered to 15 of the 17 participants. 2.2.5. Statistical analysis of comparison to the control group In order to determine for each score of each participant in each test whether it was within the normal range, we compared the score with the score of the relevant control group. Scores of participants in fifth and sixth grade were compared to the scores of controls in fifth grade. Scores of participants in seventh–ninth grade were compared to the middle school control group, and the scores of the two adults were compared to the adult control group. The comparison was done using Crawford and Howell’s (1998) t-test for the comparison of a single participant to a control group. For each task and 3 We preferred to use a lexical selection task for a word and its pseudohomophone over lexical decision of single items because on the basis of an earlier assessment (Lukov and Friedmann, 2006), individuals with surface dyslexia who perform flawlessly or almost flawlessly on lexical selection sometimes fail on lexical decision. This, we believe, results from the inclination or custom, when encountered with a letter string, to read and sound-out via the sublexical route. In the case of lexical decision of a pseudohomophone this tendency yields an existing word and thus leads to acceptance of the pseudohomophones as a word. However, such strategy cannot be employed when two items are presented, which both lead to the same sound. In this case, the reader is forced to consult the orthographic input lexicon. When this lexicon is available, lexical selection is successful.
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