Morphological spelling in spite of phonological deficits: Evidence from children with dyslexia and Otitis Media

The present study examines whether literacy or phonological impairment affects use of morphological spelling constancy; the principle that morphemes are spelled consistently across words. Children with dyslexia or otitis media (OM) were compared to chronologicalage matched children and reading-ability matched children. Monomorphemic and polymorphemic nonwords were spelled in a sentence completion dictation task. Use of root and suffix morphemes increased with age in typical development, particularly derivational morphemes. Dyslexic children generally used morphological strategies less than their chronological-age matched peers but to a similar extent as reading-ability matched. OM children showed a specific weakness in using inflectional suffixes. Results suggest different causes for the spelling difficulties in each case: dyslexic children had difficulties in generalising more complex morphological relationships, while the OM children’s difficulties had a phonological/perceptual basis. MORPHOLOGICAL NONWORD SPELLING 3 Research into literacy impairment has often focused on difficulties in acquiring phoneme-grapheme correspondence. However, English is a morphophonemic language and in order to learn to spell successfully one must associate both phonemes and morphemes with graphemes. Morphemes are spelled consistently in different words even at the expense of letter-sound correspondence. For example, the spelling of the word-final phoneme /t/ in helped is determined by “suffix constancy” – the English past-tense inflection is typically spelled + despite variation in pronunciation (e.g., helped, cleared, wanted; Nunes & Bryant, 2006). Similarly, roots are spelled consistently across words and this “root constancy” provides an explanation for many unusual spelling-sound correspondences (e.g. the spelling of ‘health’ is determined by the spelling of ‘heal’, despite variation in pronunciation; Bourassa & Treiman, 2008). Very little is known about the role of morphological knowledge in literacy impairment. The present study examines use of morphological constancy by children with literacy and phonological difficulties. The aim is to establish whether either skill constrains use of morphology. Variation in morphological skill predicts literacy in typically developing children even after accounting for phonological awareness (Carlisle & Nomanbhoy, 1993; Mahony, Singson, & Mann, 2000). The contribution of morphological awareness increases with age (Singson, Mahony, & Mann, 2000). However, there is debate as to when morphological knowledge is used in literacy, with some researchers suggesting it can be used from the earliest stages (Deacon, Pacton, & Conrad, 2008; Pacton & Deacon, 2008; Treiman & Cassar, 1996; Treiman & Bourassa, 2000) and others arguing that it must come after a more basic phonemic decoding strategy (Nunes, Bryant, & Bindman, 1997a; Nunes, Bryant, & Bindman, 1997b; Ehri, Cardoso-Martins & Carroll, 2013). The educational implications from these competing theories are significant, particularly for children who show life-long difficulties in phonological processing, such as MORPHOLOGICAL NONWORD SPELLING 4 those with dyslexia. The ability to segment speech and associate speech sounds (phonemes) with letters (graphemes) is probably the single most important skill in early word reading and spelling. Deficits in phonological awareness are linked with literacy delays and impairments (Carroll & Snowling, 2004; Snowling, 2000). ‘Decoding first’ accounts highlight the need to remediate phonology as an inevitable first step, whereas ‘all available skills’ accounts imply that alternative skills could compensate for deficits in phonology. This is clearly a crucial issue in supporting dyslexic children. Inflectional and derivational morphology are the focus of the present study. Inflection serves a primarily grammatical role, for example transformations that mark for number and tense (e.g., cat-cats, walk-walked). Inflection tends to result in relatively minor phonological/orthographic changes, adding or changing one or two phonemes/graphemes. Derivation changes word class and has greater impact on semantics and phonology/orthography. Derivation also requires more word-specific knowledge, as some alternations are less transparent (e.g., absorb-absorption) and multiple affixes can have the same meaning. For example, equality and equalness are both legal morphological constructions with the same meaning but only the former is a real word (Carlisle, 1987). Hence, in derivation, word specific knowledge must be used to select the correct target. English inflection has greater root and suffix constancy than derivation. Understanding and use of inflectional morphology appears easier and earlier than derivational morphology; Deacon & Bryant (2005) demonstrated that 6to 8-year-olds spell more inflectional suffixes correctly than derivational suffixes. It is unclear whether morphological spelling is impaired or spared in dyslexia and, in particular, whether both inflectional and derivational morphology are affected equally. Children with dyslexia have difficulty spelling, so one would anticipate that their morphological spelling will be impaired compared to chronological-age (CA) matched peers. MORPHOLOGICAL NONWORD SPELLING 5 A more relevant comparison is against literacy-ability matched peers (generally matched for reading-ability, henceforth RA), which reveals whether use of morphology in dyslexia is simply delayed or following a different trajectory (Bourassa & Treiman, 2008). Some authors have argued that dyslexic individuals have impairments in morphological constancy compared to literacy-ability matched peers. Hauerwas and Walker (2003) and Egan and Tainturier (2011) both found dyslexic children use inflectional root and suffix constancy less than both CA and RA matched peers. Carlisle (1987) showed that dyslexic adolescents (14-year-old) were less likely to spell both root and derived words correctly than younger (9-year-old) typically developing children of similar spelling ability, and were also less likely to show evidence of morphological structure. Others have argued against impaired morphological constancy in dyslexia. Tsesmeli & Seymour (2006) found that dyslexic adolescents (13 to 14-years-old) demonstrated worse performance on derivations than RA matched children and were less likely to spell root morphemes in the same way in base words and derivations. This would suggest a difficulty with derivational morphology. However, since the difference in accuracy when spelling base and derived words was of the same magnitude for dyslexic adolescents as other groups, Tsesmeli & Seymour (2006) conclude that dyslexic children did not have a specific difficulty spelling morphological derivations. Two further studies suggest that dyslexic children make literacy appropriate use of the principle of root consistency to guide spelling of both inflections (9;2 – 14;7 years old; Bourassa, Treiman & Kessler, 2006) and derivations (1018;8 years old; Bourassa & Treiman, 2008). Moreover, Hauerwas and Walker (2003) found that the extent of phonological impairment in the dyslexic group was linked to proficiency in inflectional suffix spelling. Hence, difficulties using inflectional morphology may be linked to phonological impairment rather than literacy ability per se. MORPHOLOGICAL NONWORD SPELLING 6 Overall, significant gaps and uncertainties remain in the existing literature. All previous studies were performed with adolescent poor readers, who have probably received a great deal of remediation. All previous studies used real word stimuli, as previously highlighted, word-specific knowledge is particularly important for derivational morphology but is also problematic when comparing younger and older children, since older children have had more exposures. Nonwords provide a particularly clear test of spelling strategies. Children cannot use word-specific knowledge and are forced to decompose, exposing use of letter-sound correspondence or other units such as morphemes. Nonword spelling is an established paradigm and has previously been used to illustrate typical development of inflectional morphology (Nunes, et al., 1997a) and morphological constancy in profoundly deaf children’s plural noun spellings (Breadmore, Olson, & Krott, 2012), but has not been used more broadly with other groups of literacy impaired individuals. No previous research with literacy impaired participants has examined both derivational and inflectional morphological constancy. The present study is also unique in comparing children with dyslexia to a group of children with phonological difficulties with a known cause but relatively good literacy skill (children with OM). The present study addresses these methodological issues while asking the following theoretical questions: 1) Does literacy impairment reduce use of morphological constancy in spelling? 2) Does the nature of phonological impairment influence use of morphological constancy? Experiment 1: Morphological spelling by children with reading difficulties Dyslexia affects around 10-15% of the population and is defined as a specific impairment in learning to read beyond that expected based on other available skills, aptitudes and opportunities (Vellutino, Fletcher, Snowling, & Scanlon, 2004). Classically, dyslexia was defined in terms of a discrepancy between reading and IQ, but there is now a consensus that MORPHOLOGICAL NONWORD SPELLING 7 dyslexia lies at the end of a continuum (Snowling, Gallagher & Frith, 2003) and that a discrepancy definition is not the best way to define the disorder (DSM-5; American Psychiatric Association, 2013), hence we did not limit our sample by IQ. Until recently, poorly specified phonological representations were believed to be ubiqutous within dyslexia (Snowling, 2000; Vellutino et al., 2004). Although the causes of dyslexia have more recently been argued to be multiple and probablistic, severe phonological awareness impairments are highly prevalent and persistent (Pennington et al., 2012; Peterson, Pennington, Olson, & Wadsworth, 2014). As described above, previous research on morphological spelling in dyslexia is inconsistent, making it difficult to predict performance, particularly in comparison to literacy ability matched children. Hence we present three possible hypotheses; age appropriate, literacy level appropriate, or impaired use of morphological constancy. Morphological constancy subdivides into root and suffix constancy. In this study, root constancy is measured by the proportion of spellings that contain the root as provided earlier in the sentence. Suffix constancy is measured by an increased proportion of suffix spellings in morphologically complex nonwords compared to monomorphemic control nonwords with the same final phonemes. Age appropriate morphological constancy would be demonstrated by an equal proportion of dyslexic and CA matched children’s spellings indicating root and suffix constancy. Such a finding would suggest that morphological skills are not dependent on phonological or literacy skill. Literacy level appropriate morphological constancy would be demonstrated by an equal proportion of dyslexic and RA matched children’s spellings indicating root and suffix constancy. This would suggest that dyslexic children are delayed but following the typical pattern of spelling acquisition. MORPHOLOGICAL NONWORD SPELLING 8 Impaired morphological constancy would be revealed by a smaller proportion of dyslexic children’s spellings indicating root or suffix constancy than RA matched peers. This would suggest an altered course of spelling development and that dyslexic children have a specific difficulty with morphology. There would be two possible explanations; morphological skills could be dependent on phonological or literacy skill. Experiment 2 explores these possibilities. Finally, we examine whether different patterns are observed in use of inflectional and derivational suffixes. Inflectional is more frequent and transparent, and has previously been shown to be easier and acquired earlier (Deacon & Bryant, 2005). Therefore, dyslexics might have more difficulty in using derivational morphology.