Description of the condition

Dyslexia is a specific learning disability "with a neurobiological origin marked by difficulties with accurate and/or fluent recognition and poor spelling" (World Health Organization 1992; Lyon 2003). Also known as developmental dyslexia, specific reading disability or specific learning difficulty, dyslexia is a difficulty in learning present in people with normal or higher than normal intelligence and not resulting from poor vision, hearing difficulty or a lack of socio‐environmental opportunities, lack of motivation, or even lack of adequate instruction (Shaywitz 2003). This review does not include dyslexia that is acquired, for example, due to brain injury or due to a condition such as glue ear. Dyslexia is a persistent difficulty, such that "children who fail to read adequately in 1st grade have a 90% chance of reading poorly in 4th grade and a 75% chance of reading poorly in high school" (Gabrieli 2009). Gabrieli 2009 also points out that the roots of dyslexia begin before initial reading instruction, but it is commonly diagnosed (in the United States) in children aged seven to eight years, by which time the reading difficulties are clearly measurable. According to Lyon 1996, 75% of children with reading disabilities not identified before the third grade continue to have reading disabilities into the ninth grade, and fewer than two per cent go on to participate in a four‐year higher education program after high school.

Dyslexia is strongly heritable (54% to 75%), occurring in up to 68% of identical twins and 50% of individuals who have a parent or sibling with dyslexia (Pennington 1996), and its prevalence is around 4% to 10% of school‐aged children (Shaywitz 1998; Bishop 2004; Blomert 2005), depending on the criteria applied (for example, Zoccolotti 2010 identified 17 types of developmental dyslexia). The main theory about its cause is related to a deficit in phonological processing (Bradley 1978; Wagner 1987; Ramus 2003), and more recent functional studies have revealed a hypo‐activation of the left temporo‐parietal cortex when dyslexic children are compared with typically developing readers (Hoeft 2007). Other authors, such as Kronbichler 2008 and Pernet 2009, have reported a reduction in gray and white matter in children and adults with dyslexia.

Reading can be thought of as having different components (or 'domains') and dyslexic children have problems with some of these components, such as phonological awareness and reading fluency. Phonological awareness is the ability to attend to and manipulate the sounds in words (Stanovich 1986), segmenting each individual speech sound. This awareness is important when learning to read in alphabetic script such as Spanish, German or English (Goswami 1990; Hulme 2002; Muter 2004). Reading fluency is most often defined as the ability to read text quickly, accurately, and with appropriate expression (National Reading Panel 2000; Kuhn 2003) and oral reading fluency has been shown to be related to comprehension (Fuchs 1988; Fuchs 2001; Jenkins 2003). Dyslexic children often have difficulty with this reading fluency domain, which results in poor comprehension. Recently, this domain was identified as an area of difficulty for individuals with dyslexia by the International Dyslexia Association (Lyon 2003). The reading process is slow and laborious for dyslexic children (Chall 1990) and may be followed by an avoidance of reading and general frustration (Pinnell 1995; Leinonen 2001).

Description of the intervention

This review is concerned with the potential effect that school‐based musical training (or music education) can have on children's reading. Here we consider music education as any methodology of teaching music, whether in a specific center of music teaching (for example, conservatory, Music School) or a single music class included in the syllabus of a kindergarten or elementary school. Generally, musical training or music education (both terms will be used interchangeably in this review) can be described as the process of learning music, supervised by a music teacher or a specialist in music education. A music teacher is defined as someone who has an understanding of the elements of music context, score analysis, musical style and aesthetics and is competent to teach this to children. There are different approaches to music education (Suzuki, Dalcroze, Orff and Kodály) and students are generally exposed to key elements of music such as rhythm, melody, harmony and timbre regardless of the approach, although each one has its own particular form. The main approaches to music education currently are:

• Suzuki Method: developed by Shin´ichi Suzuki (1898‐1998), a Japanese educationist and violin teacher, who believed that children could learn musical skills at an early age, initially through listening, and observed the way young children acquire language through hearing others speak (Mills 1973). Just as children learn to speak before learning to read, Suzuki advocated a delay in teaching musical notation until there was an adequate grounding in playing skills and the development of musical memory. In the Suzuki Method, the children are taught in groups rather than individually, encouraging cooperation and teamwork.

• Dalcroze Method: created by the Swiss musician and educator Emile Jaques‐Dalcroze (1869‐1950) who developed a system of group music teaching through ‘gymnastique rythmique’(eurhythmics). This system uses physical exercises together with the music class to help students respond physically and aesthetically to music (Henry 1958).

• The German Orff‐Schulwerk system, created by Carl Orff, which combines choral singing, aural training, movement, improvisation and activities that use specially designed pitched and non‐pitched percussion instruments. Five books of teaching materials, Musik für Kinder (1950‐54), exemplify ways of making what is called "elementary music". Various arrangements of folk songs and traditional melodies are intended as models or suggestions for teachers rather than a comprehensive scheme (Keller 1963).

• Kodály's principles of music teaching (Hungarian Method) are in many ways similar to those of Orff, but the Hungarian approach is more fundamentally choral. Concerned with the development of inner hearing and musical literacy, and determined to improve the musical life of the nation, Kodály drew on his country's folk song tradition, which he combined with art music using the pitch teaching principles of Curwen, hand signs and the rhythmic language of the Galin‐Paris‐Chevé movement (Sándor 1975).

In music education, each one of the musical elements (rhythm, timbre, aesthetic, harmony, pitch) can be studied and developed separately through different strategies in order to stimulate and develop children’s perception of them as shown by Moreno 2009. Studies vary in the frequency and length of sessions, for example, Overy 2003 studied 20 minute singing‐based music lessons delivered three times a week. Research has been conducted using different methodologies of musical teaching as a basis for musical practice, where multisensory and developmental group activities are presented to the children. Some activities may involve singing (all the children together singing the same musical passage, in unison, or in canon structure), rhythm (via corporal movement or corporal percussion) and instrumental practice (either highly technical in learning a specific musical instrument or using the instrument only as a form of interaction between the musical sheet system and the children).  

The National Association for Music Education, whose mission is to advance music education by encouraging the study and making of music by all, has established nine national standards for Music Education (MENC 2010).

1. Singing, alone and with others, a varied repertoire of music.
2. Performing on instruments, alone and with others, a varied repertoire of music.
3. Improvising melodies, variations, and accompaniments.
4. Composing and arranging music within specified guidelines.
5. Reading and notating music.
6. Listening to, analyzing, and describing music.
7. Evaluating music and music performances.
8. Understanding relationships between music, the other arts, and disciplines outside the arts.
9. Understanding music in relation to history and culture.

It is important to emphasize that musical training is not the same as music therapy, despite the fact that both use music as an intervention and both are often provided in the same setting. Music therapy is a psychotherapeutic method that uses musical interaction as a means of communication and expression and aims to help people with mental illness to develop relationships and to address issues they may not be able to address using words alone (Gold 2004; Gold 2009).

How the intervention might work

Studies correlate children's ability to read with their ability to distinguish pitches accurately (Fisher 2001; Hansen 2002; Schön 2004; Magne 2006; Besson 2007; Marques 2007; Nikjeh 2009), arguing for a strong link between basic auditory perception abilities and reading abilities. Anvari 2002 found significant correlations between music skills, phonological awareness and the reading development of four‐ and five‐year‐old children. The connections between reading achievement and two distinct styles of music education have been investigated: (a) Orff, Kodály or Dalcroze instruction, which stresses multisensory, developmental group activities emphasizing singing or playing percussion (Hurwitz 1975), or (b) participation in choral, band, or orchestral ensembles requiring music reading skills and extensive practice to achieve competence (Douglas 1994). Nikjeh 2009 observed that trained musicians, when compared with non‐musicians, showed more efficient neural detection of pure tones and harmonic tones, and demonstrated superior memory for acoustic features of pure tones, harmonic tones, and speech. Growing evidence from a range of research disciplines suggests that musical experience can have a positive effect on language and literacy abilities (Douglas 1994; Sutton 1995; Kilgour 2000). In addition, there is increasing recognition of the numerous shared features of music and language, from developmental characteristics to perceptual processes and common neural substrates (Sloboda 1985; Patel 1998).

According to Schlaug 2005, playing an instrument requires a range of skills, including reading a symbolic system (musical notation) and translating it into sequential, bimanual motor activity dependent on multisensory feedback. Learning to read, according to this point of view, could be compared to playing or learning a musical instrument, because it requires coordination of the eye muscles to follow a single line of printed musical notation (for example, when playing the violin, viola, bass, or flute) or a conjunction of lines (for example, when playing the piano, organ, or harpsichord). It is necessary to develop a spatial orientation to play each musical note from the sheet music and correlate it with a specific position on the instrument, which is comparable in this case with words and letters that together form a larger structure.

Temporal cues are important in speech perception (Martin 1986), and temporal fluency is a key factor in reading proficiency (Hanes 1986). More specifically, according to Huss 2010, musical metrical sensitivity has been found to be a predictor of phonological awareness in reading development. In this context, Besson 2007 observed that, as result of musical practice, a set of common processes may be responsible for pitch processing in music and in speech. Accordingly, it would be reasonable to assume that if pitch ‐ the perceptual attribute that corresponds to sound frequency ‐ is an important acoustic parameter for both music and speech perception, then increased efficiency in pitch processing due to musical expertise should also improve pitch perception in speech. Overy (Overy 2000; Overy 2003), on the other hand, focused her hypothesis on the temporal processing component. According to this author, dyslexic people have particular difficulties with skills involving accurate or rapid timing, including musical timing skills. It has been hypothesized that musical training may be able to remediate such timing difficulties, and have a positive effect on fundamental perceptual skills that are important in the development of language and literacy skills. Gabrieli 2009 has pointed out that dyslexic children who retain their benefits after systematic instruction in phonological awareness and decoding strategies improve from year to year, but they do not catch up with the typical reader; according to the same author, improvements are more likely to occur in children who are beginning to read (ages six to eight) than in older children.

Why it is important to do this review

Several studies have reported positive associations between music education and enhanced abilities in non‐musical (for example, linguistic, mathematical, and spatial) domains in children (Schellenberg 2004; Piro 2009), although the knowledge about this topic is non‐specific and contradictory. It is therefore important to critically analyze and synthesize the evidence for the effectiveness of musical training as a means of improving reading in those children with dyslexia.