Hahn, N., Fox, J. J., & Molholm, S. (2014). Impairments of multisensory integration and cross-sensory learning as pathways to dyslexia. Neuroscience and Biobehavioral Reviews, 47, 384–392. doi:10.1016/j.neubiorev.2014.09.007
This article discusses the role of auditory and visual processing in learning to read. The fundamental argument is that learning to read requires integration of information across these two sensory modalities. Through the auditory modality, speech is processed and phonemic representations of speech are formed; in the visual modality, written words and specific orthographic patterns enter the brain. Learning to read represents the formation and connection of phonemic and orthographic representations, which the authors suggest is a cross-modality source of difficulty in dyslexia.
In an examination of the literature, the authors argue for multisensory deficits in dyslexia. They cite older literature involving auditory-visual integration in dyslexia (Birch & Belmont, 1964), where people with dyslexia struggle to match similar patterns presented to the auditory and visual modalities. Not cited is evidence that these tasks are weak predictors of reading failure (Satz, Taylor, Friel, & Fletcher, 1978). Another type of study examines the binding of speech sounds and graphemes, which develops more slowly in dyslexia and may lead to automaticity deficits (Blau, van Atteveldt, Ekkebus, Goebel, & Blomert, 2009). These studies are sparse and seem to imply a more general associative learning deficit in dyslexia. Less support is found from studies of audiovisual speech integration in dyslexia. A major source of cited support is found in studies that use multisensory training in dyslexia, represented as linking phonemic representations of words with graphemic symbols; also cited is the National Reading Panel (2000) conclusion that phonological awareness training is more effective when letters are used. Finally, literature involving functional and structural neuroimaging is cited that shows reduced connectivity between the brain regions that process phonological and orthographic components of words.
Acknowledging that the evidence base is weak, the conclusion is that there are multiple pathways to the behavioral phenotype of dyslexia, one of which is weak multisensory integration.
In a sense, the problems the authors describe are metaphors for learning to read. It is clear that to learn to read, young children (or an adult illiterate) must take what they have learned in processing speech and connect it to words. Reading involves an explicit understanding that words are composed of phonemes (i.e., phonological awareness) and that the key to representing words in reading is to link what words sound like with what they look like (alphabetic principle). Brain systems that mediate sublexical (phonemic) and orthographic processing, the latter eventually at a lexical or whole-word level, develop in typical readers. These systems develop to a lesser degree in dyslexia, but the sublexical problem is primary and the lexical problem is at least in part a product of reduced reading experience. Fundamentally, much of the literature cited by Hahn, Fox, and Molholm (2014) is just a description of reading that invokes the primary sensory modalities, but they don’t establish the necessity of linking the sensory modalities themselves.
People with dyslexia do have trouble linking phonetic representations of words with graphemes that represent words. But they don’t uniformly have problems at the level of a primary sensory deficit, and forming phoneme-grapheme associations is not the same as linking auditory and visual modalities. We don’t hear or actively process words through the auditory modality as we read; in fact, auditory feedback of this sort would make reading more difficult. Reading is fundamentally processing print in the visual modality; explicit use of the auditory modality is distracting. It is possible that difficulties with speech perception interfere with both language and reading development, but characterizing this as an auditory processing deficit leads to interventions that slow speech (e.g., FastForWord) or reduce noise during speech processing, neither of which is associated with better reading (Pennington, 2011; Snowling, Gooch, McArthur, & Hulme, 2018). Citing problems with learning phoneme-grapheme correspondences and evidence of learning to read better when phonemes are paired with letters provides descriptions of the problem with reading, not evidence of multisensory deficits. In a sense, the evidence for multisensory deficits cited by Hahn et al. is tantamount to saying that people with dyslexia have trouble learning to read.
Where the term “multisensory” becomes especially confusing and controversial is in reading programs described as “multisensory.” Such programs, which are often represented as "Orton-Gillingham” or “multisensory,” are often believed to be specifically tailored to students with dyslexia. The programs that get this label require presentation across sensory modalities to enhance the formation of memories. It’s a term often associated with programs deemed most appropriate for people with dyslexia, sometimes in legislation.
It is important to recognize that although early versions of these programs emphasized the need for instruction to all sensory modalities, this was often not in the context of reading or writing. The programs have evolved to an emphasis on learning about the structure of language, especially the phonological and morphological internal components of words. Contemporary “multisensory” structured language instruction embeds knowledge about the structure of language in five approaches to instruction: (1) simultaneous, teaching to sensory modalities (visual, auditory, kinesthetic) to enhance memory and learning; (2) systematic, cumulative organization of material; (3) explicit, teacher-directed instruction through continued teacher-student interaction; (4) ongoing assessment of individual student needs; and (5) both analytic (presenting the whole and breaking it down into constituent parts) and synthetic (putting parts of language together to form a whole) approaches to phonics (Birsh, 1999).
Although there is good evidence for principles 2–5 (see Fletcher, Lyon, Fuchs, & Barnes, 2018, Chapter 5), the multisensory component remains confusing and controversial. It is difficult to provide a precise definition of the multisensory component and little evidence that it is an essential part of reading instruction. Studies comparing reading instruction with and without the traditional multisensory component (i.e., practice in the auditory, visual, and kinesthetic modalities) have not found a difference in outcomes (Clark & Uhry, 1995; Moats & Farrell, 1999; Wise, Ring, & Olson, 1999). However, most effective reading programs require students to pronounce sounds and words accurately and quickly for automaticity, often also requiring writing of words. Guidelines for educational therapists focusing on dyslexia require knowledge of multisensory instruction to different sensory modalities but place it in the explicit context of reading and writing (e.g., Center for Effective Reading Instruction standards). Thus, students hear a word, say the word, read the word, and write the word. In these standards, there is more emphasis on explicit, teacher-directed instruction, assessment of learning needs, and the structure of language. This component is better described as multimodality, not multisensory. Multimodality characteristics are represented in many effective approaches to reading instruction and not specific to children with dyslexia. In general, children with dyslexia learn to read like other children but need more time on task, differentiation, and intensity.
One reason to avoid linking multisensory approaches specifically to dyslexia, especially in legislation, is that programs identified as “multisensory” do not have a strong basis in evaluation research (National Reading Panel, 2000), especially compared to their implementation. Ritchey and Goeke (2006) identified 12 experimental and quasi-experimental evaluations of “multisensory” reading programs. The average effect size for the efficacy of the programs was moderately large for word attack and comprehension skills and small to moderate for word recognition skills. Outcomes tended to be a little larger for multisensory programs, but the effect size estimates of efficacy were not based on strong research designs. Some studies generated effect sizes that were minimal and may not hold in a large study with an experimental design. Only one study used an experimental design with random assignment, and it did not generate strong evidence of efficacy. Ritchey and Goeke suggested that despite wide acceptance and enthusiasm for the programs, not all studies reported them to be effective, much less superior to other programs, highlighting the absence of experimental studies. It is clear that effect sizes for evaluations of reading programs are lower as experimental designs with larger samples are employed (Scammacca et al., 2016).
The other reason to think carefully about the term “multisensory” is that it can be used to restrict the range of program types available to children with dyslexia or children who have decoding problems and are not identified with dyslexia. Not all approaches are effective with every child. Many programs appropriately avoid a major focus on teaching outside the context of reading and writing even though they teach to multiple modalities. Direct instruction approaches, for example, are explicit, systematic approaches to decoding instruction (as well as fluency and comprehension) and have strong evidence of efficacy for poor readers (Stockard, Wood, Coughlin, & Khoury, 2018). Many other programs have evidence of efficacy for children identified with word-level reading disabilities or dyslexia (see Fletcher et al., 2018). Tying dyslexia to a specific type of program restricts access to these effective programs.
The key question is not whether a program is multisensory, but whether the program teaches decoding explicitly, is comprehensive (has components that teach decoding, fluency, and comprehension), and allows the instructional component to be differentiated for individual student needs. The program needs to attend to the alphabetic principle and explicitly teach the relation of what words sound like and what they look like, but there are many methods for accomplishing this task. In the end, the question is the evidence for effectiveness with children identified with dyslexia.
This does not mean that all reading programs are effective. Programs that de-emphasize the alphabetic principle; teach phonics incidentally, as needed, or as one of three cueing systems; teach only phonics; teach reading as a discovery process that is teacher facilitated, not teacher directed; balance phonics and comprehension with no integration or differentiation; or are not explicit approaches to instruction are not effective for children with dyslexia. Similarly, approaches to instruction that focus on remediation after grade 3 and not prevention in kindergarten to grade 2 are clearly less effective because the child has not been able to access print and can’t get enough reading experience to program the neural systems needed to mediate skilled reading (Fletcher et al., 2018).
Reading prescriptions for children with dyslexia, especially in legislation, should define the characteristics of effective approaches, not a brand or program or component. Restricting dyslexia to multisensory-branded approaches, especially given the weak evidence base in Hahn et al. (2014) and Ritchey and Goeke (2006), will make it much more difficult to prevent and remediate this common source of reading disability.
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Blau, V., van Atteveldt, N., Ekkebus, M., Goebel, R., & Blomert, L. (2009). Reduced neural integration of letters and speech sounds links phonological and reading deficits in adult dyslexia. Current Opinions in Biology, 19, 503–508.
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