Psychomusicology: Music, Mind & Brain 2011, Vol. 21, No. 1 & No. 2 © 2012 by Psychomusicology DOI: 10.1037/h0094002 Singing development as a sensorimotor interaction problem C H R I S T I N E D. T S A NG Huron University College at the University of Western Ontario R AY N A H . F R I E N DLY & L AU R E L J. T R A I NOR McMaster University a b s t r ac t—Singing is a ubiquitous human behavior and plays a signiicant role in human culture and socialization. Research on children’s singing has focused on music instruction techniques for developing singers, yet little is known about the developmental mechanisms underlying singing acquisition. Recently, Berkowska and Dalla Bella (2009a) proposed a sensorimotor loop model of singing to explain poor singing ability in the adult population. Here, we review the literature on the development of singing during childhood in the context of the sensorimotor loop model of singing. k e y wo r d s —singing, development, children, auditory perception, motor function Singing is widely regarded as a universal human behavior (Dowling, 1984; Welch, 1994) that serves a number of important social functions. Singing is an effective means of transmitting cultural knowledge and social customs (Chatwin, 1987; Cong-HuyenTon-Nu, 1979). Singing is also used to ease the pressures of everyday life. For example, many workers use song to accompany work activities, especially those requiring the synchronization of repetitive movements (Cong-Huyen-Ton-Nu, 1979; Keil, 1979). Singing is often an important part of courtship, and it has been proposed that robust musical calls may signal the possession of healthy, appealing genes to prospective mates (e.g., Huron, 2001). In general, singing can promote social cohesion, reinforce cherished values and ideals, foster shared identity, and promote “emotional contagion” (Booth, 1981; Peretz, 2006). Finally, singing plays a critical role in child rearing and the caregiver-infant bond. Lullabies and playsongs are found in all known cultures, suggesting that they serve an important function in maternal child care (Trehub, 2000; Trehub & Trainor, 1998). Despite the importance of singing in both human development and human culture, there has been relatively little empirical research on the acquisition of singing during childhood. Singing is thought to emerge spontaneously without formal instruction during early child development (Dalla Bella, Giguere, & Peretz, 2007) and many studies over the last 30 years have documented a relatively orderly progression of the acquisition of speciic singing abilities during childhood (e.g., see Welch, 2006 for a review). However, the developmental mechanisms underlying singing acquisition during childhood are still not well understood. Although there is general agreement that both maturational and experiential factors affect singing development (e.g., Davidson, McKernon, & Gardner, 1981; Stadler-Elmer, 2006; Welch, 1985), there are few empirical studies of how these factors interact. Welch (1986) proposed a model of singing acquisition in which children’s singing behaviors appear in a ixed order from Stage 1, where the words of a song are the initial center of interest rather than the melody, to Stage 5, where there are no signiicant melodic or pitch errors in a child’s vocal productions. Presumably this progression Christine D. Tsang, Department of Psychology, Huron University College at the University of Western Ontario; Rayna H. Friendly and Laurel J. Trainor, McMaster University Correspondence concerning this article should be addressed to Christine D. Tsang, Department of Psychology, Huron University College at the University of Western Ontario, London, ON, Canada, N6G 1H3. Email: ctsang33@huron.uwo.ca 31 Christine D. Tsang, Rayna H. Friendly, & Laurel J. Trainor is impacted by culture, practical experience, and genetically-driven maturation. Detailed study of singing development requires, irst, a deinition of singing and, second, a notion of what constitutes mature singing behavior. With respect to the irst question, Welch (1994) noted that the judgment of an utterance to be speech or song “is deined by a complex web of interacting factors encompassing perception, cognition, physical development, maturation, society, culture, history and intentionality” (p. 3). Early in development, singing and talking may be less differentiated than later. Indeed, infant-directed speech is often referred to as musical speech because of its exaggerated pitch contours, rhythmic patterning and repetition (Fernald, 1991). The boundaries between speech and song can be even less clear in the vocalizations of infants and young children, and determination is muddied by the fact that adults often attempt to over interpret infant vocalizations (Welch, 1994). Compared to young children and adults, infants show a relatively large vocal range (between 195 Hz and 1035 Hz) that is quite stable over the irst year of life (Fox, 1990; Moog, 1976), and several studies have observed that the majority of infant vocalizations show descending melodic contours (Jersild & Bienstock, 1931; Michel, 1973; Moog, 1976; Reis, 1987). An analysis of infant vocalizations also indicates that the vocalizations are “rhythmically amorphous” (Moog, 1976). According to Welch (1994), the earliest phase of singing development is the “babbling song” phase, in which the infant sings in a continuous voice, “during which pitch glides (glissandi) are made over several musical pitches in a repetitive manner” (p. 4). Based on Welch’s (1994) timeline of song development, as infants’ facility with language develops, words and song fragments take early precedence, with rhythm and pitch developing afterwards. During this time, infants become enculturated to their native linguistic and musical systems (Hannon & Trainor, 2007), as well as to their social world (Carpendale & Lewis, 2004). This enculturation is relected in children’s invented songs, which have been found to contain phrases with distinct “beginnings and ends”, usually in 2-bar or 4-bar phrases (Davies, 1992). 32 This suggests that children have an understanding of the structural organization of songs. By the time they enter school at age 5 or 6, children generally follow a similar learning hierarchy as adults, such that the words of a song are usually learned before the rhythmic structure, which in turn is followed by pitch learning (Davies, 1992; Welch, 1994). With respect to the deinition of what constitutes mature singing behavior, proiciency in adult singing is often measured in terms of pitch accuracy (Berkowska & Dalla Bella, 2009a; 2009b; Dalla Bella et al., 2007), although there is of course much more to singing than this. There is clearly a wide range of singing ability in the adult population (e.g., Amir, Amir, & Kishon-Rabin, 2003; Pfordesher & Brown, 2007). Approximately 15% of the general population have been estimated to self-label as “tone deaf” in that they believe themselves to have a musical disability (Cuddy, Balkwill, Peretz, & Holden, 2005); however, it is likely that less than 5% of the general population actually possess a musical learning disability, or congenital amusia (Sloboda, Wise, & Peretz, 2005). While “tone deafness” refers to a perceptual deicit, it is also often used to describe poor singing ability (Sloboda et al., 2005), which implicitly suggests that deicits in perception underlie poor singing ability. However, as discussed below, this is often not the case. What causes poor singing? Berkowska and Dalla Bella (2009a) proposed a vocal-sensorimotor loop model of singing in which auditory pitch information is mapped onto vocal-motor movements during singing. The singer continually self-monitors the sung output, comparing it with an internal representation from memory. According to this model, singing begins with retrieval of pitch and temporal information from memory. The recalled pitches of the melody are then mapped onto representations for motor control of the vocal tract, which in turn activate motor planning areas, and subsequently enable singing output. Auditory feedback of the performance is constantly monitored by perceptual processes that compare the intended melodic output with the performance output so that on-line corrections can be made. External cues in the auditory environment also play a role in proicient singing. Errors in pitch Singing development production accuracy are minimized when singers sing along with the melodic pattern to be imitated (Pfordesher & Brown, 2007). Accordingly, the vocal sensorimotor loop model suggests that memory, motor skill, perception and feedback (internal as well as external) are all involved in proicient pitch singing. It is possible that the majority of poor pitch singers have accurate perceptual skills or accurate perceptual and motor skills, but show impaired integration between perception and motor skill. In other words, the major cause of poor pitch singing may lie in the linkage between perception and action, and poor-pitch singing may often be a result of a mismapping of stored pitches onto motor gestures. Many components of the vocal sensorimotor loop begin to develop during infancy, but take a long time to reach maturity. There is much evidence to suggest that basic vocal motor skills are on-line by 7 months of age, when reduplicative vocal babbling typically emerges (Locke, Bekken, McMinn-Larson, & Wein, 1995), although the physiological components of voice (e.g., larynx and associated muscles, lung and rib capacity) develop considerably between the preschool years and adolescence (see Trollinger, 2003). Reasonably good auditory perception abilities are also present during infancy, although adult pitch discrimination thresholds are not achieved until about 10 years of age (Jensen & Neff, 1993; Maxon & Hochberg, 1982; Thompson, Cranford, & Hoyer, 1999). Perceptual skills, such as combining harmonics to form a sensation of pitch are present by 4 months of age (He & Trainor, 2009), and young infants can discriminate the pitch of complex tones that are a quarter tone apart (Trainor, Lee, & Bosnyak, 2011). Indeed, infants have quite sophisticated perception abilities related to music (for a review, see Trehub, 2010). Sensorimotor integration abilities in speech development also emerge in the irst year after birth (e.g., Westermann & Miranda, 2004). In the context of musical rhythm, auditory-motor integration also develops early, such that passive movement has been found to affect auditory meter interpretation in 7-month-old infants (Phillips-Silver & Trainor, 2005). However, sensorimotor integration continues to develop well into middle childhood and adolescence and depends on the maturation of general cognitive abilities such as recognition memory (e.g., Luciana & Nelson, 1998), abilities that are also present during infancy (e.g., RoveeCollier, 1999), but improve over a long timeline (see Schneider & Pressley, 1989, for a review). In sum, the primary requirements of the sensorimotor loop model are present early in life, but show long developmental trajectories. In the present paper we provide a review of the experimental evidence on the development of singing during childhood in the context of the sensorimotor loop model. We focus on observed age-related differences reported in the literature, paying particular attention to implications for the sensorimotor interactions required for good singing to emerge. d e v e l o p m e n t o f vo c a l q ua l i t y, pitch r ange, and use of song The origins of both speech and singing can be seen in early infant vocalizations. Dowling (1984) observed that vocal play by infants during the babbling phase marks the onset of singing development, although it is not until the age of two years that children’s singing becomes reliably distinct from speech. Dowling proposed that singing usually arises as part of a social act, and typically consists of simple and repetitive musical phrases. Physiologically, the speaking voice and singing voice both recruit the same breathing, throat, vocal folds and larynx mechanisms, although some evolutionary theorists have claimed that singing and speaking behaviors may relect different articulatory and physiological functions, especially during childhood (Brown, Martinez, Hodges, Fox, & Parsons, 2004). A recent study comparing children’s speech and song found that the voice quality of 10-year-old children’s voices, as rated by trained raters, were perceptually similar for both speaking and singing tasks, supporting the notion that the same physiological mechanism generates both speech and singing behaviors in children (Rinta & Welch, 2009), although it should be noted that there are no comparable studies in the adult 33 Christine D. Tsang, Rayna H. Friendly, & Laurel J. Trainor literature. General measures of children’s singing ability, such as voice quality, vocal range and the degree to which children use their singing voices, show changes across age. For example, adult raters, using a qualitative descriptive scale, rated children in Grade 3 as having better voice quality when singing melodies compared to children in Grade 1 (Hanna, 1999). Similarly, a two-year longitudinal study found that children showed improved voice quality when singing recently learned songs (as measured in the context of singing tone and pitch accuracy) at age 6 compared to age 4 (Leighton & Lamont, 2006). Additionally, an acoustic analysis of the long-term average spectra of children’s singing voices showed progressive and statistically signiicant changes between 4 and 11 years of age, such that older children had increased overall vocal intensity (i.e., could sing louder) and also produced relatively more energy at harmonics below 5.75 kHz compared to younger children (Sergeant & Welch, 2008). These acoustic differences in the singing voices of children across this age range are likely due to physical growth, especially to lung and rib cage capacity (Sergeant & Welch, 2008). Vocal range (i.e., the minimum to maximum pitch that can be vocally produced) has been found to be affected by both singing experience and musical context. Although the average spoken pitch lowers with age (Welch et al., 2009), children’s mean comfortable singing range expands from about one and a half octaves (G3 to C 5) at age 7 to about two octaves (F3 to Eb5) at age 10 (Welch et al., 2009). Studies indicate that while a child’s speaking pitch is determined mainly by age, the ability to sing pitches is a complex, learned skill, and that the age at which children can match the pitch of a model is dependent on singing experience (Levinowitz et al., 1998; Phillips, 1992). Jersild and Bienstock (1931) reported that as early as age 4, some children’s vocal ranges were similar to those of the average adult, but that they were not always as capable as adults in using this range in songs. Furthermore, providing children with singing practice increased the average number of distinct tones they could sing by 30%. Singing voice use, another general assessment of singing focusing on the relative amount the singing 34 voice is used compared to the speaking voice when participating in singing tasks, has also been found to show changes with age. The use of singing voice by children is generally found to increase as children get older, although there appears to be disagreement in the age range over which this occurs. For example, Rutkowski and Snell Miller (2003) found an increase in singing voice use with age between Grades 1 and 3 whereas Welch et al. (2008) found an increase between Grades 3 and 6. Hornbach and Taggart (2005) also found that singing voice use increased from kindergarten to Grade 2, but not in Grade 3. It should also be noted that some studies have reported marginal or no consistent increases in the use of singing voice with age (Levinowitz et al., 1998; Mang, 2006). These inconsistencies across studies may be due in part to the inluence of tonal or non-tonal languages, such that Cantonese-speaking children appear to acquire the use of singing voice earlier than Cantonese-English bilingual children (Mang, 2006). This inding suggests that pitch-based experiences (such as those found with learning tonal languages) affect singing behavior. In sum, children’s singing production, as measured by vocal quality, range, and the proportion of time that the singing voice is used, appears to increase with age. The indings that children’s singing production is affected by context and training are consistent with a vocal sensorimotor loop model of singing in which practice is necessary in order to establish the detailed linking between perception and action needed for good singing ability. s i n g i n g ac c u r ac y: p i t c h - m at c h i n g There are numerous studies examining the development of pitch-matching abilities, many of which come from the music education research literature (e.g., Cooper, 1995; Davies & Roberts, 1975; Demorest, 2001; Demorest & Clements, 2007; Flowers & Dunne-Sousa, 1990; Geringer, 1983; Goetze & Horii, 1989; Green, 1994; Howard & Angus, 1997; Leighton & Lamont, 2006; Mang, 2006; Porter, 1977; Trollinger, 2003; Welch, Singing development Sergeant, & White, 1996, 1997, 1998; Yarbrough, Green, Benson, & Bowers, 1991). Accuracy in pitchmatching (as well as interval and melody matching) requires skills in both auditory perception and vocal-motor production, and is the predominant indicator used to assess singing proiciency in both children and adults. Poor pitch accuracy when imitating sung melodies is labeled as poor singing while high pitch accuracy is labeled as good or highly proicient singing. Good pitch-matching skill appears to arise without formal training or instruction in the majority of the normal population (Bentley, 1969), and the literature indicates that despite great individual variability in the singing ability of children, there is generally an improvement with age in pitch-matching ability, especially during the elementary school years. For example, Petzold (1966) reported increased accuracy of pitch-matching occurring between the irst and second grade. Geringer (1983) also found signiicant differences between pitch-matching abilities of Grade 1 versus Grade 4 children, such that fourth graders were more accurate on pitchmatching tests compared to irst graders. This is consistent with Yarbrough et al. (1991) who found that pitch-matching accuracy was signiicantly better in eighth graders compared to irst graders, although signiicant differences were not found across narrower age ranges (i.e., irst vs. second graders or seventh vs. eighth graders). In a crosssectional study of pitch accuracy in children in Grades 1 through 6, Green (1990) found that Grade 1 children showed the most errors, with improvement in pitch accuracy increasing with grade level to Grade 5. Interestingly, Grade 6 children showed a decrease in pitch accuracy compared to Grade 4 and 5 children. However, this decrease has not been replicated in children of this age group and should be interpreted with caution. In a 3-year longitudinal study, Welch et al. (1996, 1997, 1998) found that although children between the ages of 5 and 7 showed little improvement in pitch accuracy on two criterion songs taught to the children at the start of the study and assessed each year, when the pitch elements were deconstructed into simpler musical tasks (single pitch matching, pitch glides, pitch matching of melodic fragments), children showed improvement on the tasks in each year of the study. Together, this body of research suggests that age plays a signiicant role in the development of pitch-matching abilities. Although pitch accuracy depends on age, it can also be affected by environmental factors such as culture. Cross cultural comparisons have found that irst grade Chinese children show better singing abilities compared with American irst graders (Rutkowski & Chen-Haftek, 2000), a difference that might be due to increased pitch experiences due to the use of a tonal language (e.g., Cantonese). Formal music instruction also likely plays a role in improving pitch accuracy. Apfelstadt (1984) found that kindergarten children receiving vocal instruction through visual and kinesthetic reinforcement or imitation alone showed improvement in singing pitch accuracy over children learning songs by repetition and practice without direct vocal instruction. There were no differences in pitch discrimination abilities in children across instruction group, although this may have been due to a lack of sensitivity of the pitch discrimination task used in the study or to the lack of appropriate control conditions (the differences may also be attributable to music instructor differences rather than music instruction difference), or to the use of relatively small samples sizes (the control group contained only 15 children while the experimental groups each contained 24 and 23 children). Persellin (1994) also reported differences in pitch-matching accuracy of preschool children depending on learning modality. Children instructed to listen and sing along to the music performed better on a vocal pitch-matching task than did children who were instructed using visual aids (but did not sing along to the music) and children who were instructed to move to the music (but not sing along). While these results suggest that singing pitch accuracy is related to perceptual processing, these results should be treated cautiously, as this study did not report random assignment to group, nor did the study control for possible teacher effects or previous musical experience. More broadly, kinesthetic cues, such as children’s use of gesture during singing, have also been shown to improve children’s pitch accuracy (Liao, 2008; Liao 35 Christine D. Tsang, Rayna H. Friendly, & Laurel J. Trainor & Davidson, 2007). In a within-subjects design, 5- to 6-year-old children sang six different 3-note tonal patterns, with and without gesture. Based on trained raters assessments of singing pitch accuracy, it was found that children sang more accurately when the singing was accompanied with gestures (Liao, 2008). Liao and Davidson (2007) also found that the use of gesture in children was particularly effective when increasing the dificulty of the song to be sung (e.g., large pitch leaps, singing in a higher register, or singing high notes). Although it should be noted that children’s improvement in singing accuracy while using gestures may be due to greater enjoyment and better attitude in the singing and gesture condition, these results support the notion implied by the sensorimotor loop model that singing pitch accuracy is associated with motor abilities. In sum, the current research suggests that children’s singing accuracy is highly dependent on age, and that environmental context and training contribute to improvements in pitch accuracy skills. The sensorimotor loop model of singing suggests that maturational factors related to age (such as improvement in memory, improved motor skill and control) will affect singing proiciency. The model also suggests that external factors, such as culture, language, training, and motor action may also promote proicient singing development, and that practice is needed to fully develop the auditorymotor interactions needed for accurate pitch production. However, more research is needed in order to better understand the roles of experience and practice on age-related components of singing skill. p e rc e p t i o n o f t o na l i t y and singing in k ey Perceptual abilities are critical to children’s musical understanding, and children’s receptive musical competence develops without formal music training. Traditionally, the ability to sing in tune was thought to depend mainly on the perception of the pitch of isolated tones or tone pairs (Sloboda et al., 2005), resulting in the label “tone deafness” for 36 poor singing ability. However, proicient singing also relies on the perception of tonality and an understanding of the pitch structures used in the musical system in one’s culture. Whereas singing “in tune” generally refers to singing pitch accuracy and does not require any knowledge of musical key, singing “in key” requires an understanding of key membership (i.e., whether or not a note belongs to the key in which the melody is composed) and harmony (what chords accompany a melodic line). There is little cross-cultural work in this area. However, perceptual sensitivity to the particular key and harmonic structures used in Western music develops over several years through everyday exposure to Western music (Trainor & Corrigall, 2010). For example, Western adults are much better at detecting changes in a melody that go outside the key or implied harmony of that melody compared to changes that remain in the key and implied harmony. However, 8-month-old infants are equally sensitive to in-key and out-of-key changes, suggesting that infants do not yet possess an understanding of key membership (Trainor & Trehub, 1992). By 4 years of age, children have acquired knowledge of key membership (Corrigall & Trainor, 2010; Trainor & Trehub, 1994), and show rudimentary evidence of harmonic sensitivity, using both behavioral measures (Corrigall & Trainor, 2010) and electrophysiological measures (Jentschke, Koelsch, Sallat, & Friederici, 2008), although harmonic sensitivity continues to develop for several more years in the absence of formal musical training (e.g., Costa-Giomi, 2003; Morrison, Demorest, & Stambaugh, 2008). Empirical evidence demonstrating the importance of tonal perception to the development of singing in children includes the inding that children’s singing is affected by tonal or melodic context (Flowers & Dunne-Sousa, 1990; Mang, 2006). Just as the perception of tonal structure develops during childhood, so does the ability to stay within key and maintain a tonal center while singing (Flowers & Dunne-Sousa, 1990; Mizener, 1993). Flowers and Dunne-Sousa (1990) assessed preschool children’s ability to maintain a tonal center, using a rating scale designed to assess singing accuracy and tonality. Tonality was Singing development measured in terms of singing modulations of +/– 50 cents from the sung model while singing both selfchosen and learned songs. Although no signiicant age-related differences in tonality were found when 3- to 5-year-old children were singing learned songs, older children were better at maintaining a consistent key more often than younger children. When singing self-chosen songs, tonality was bestto-worst for 4-, 5-, and 3-year-olds, respectively, as measured by number of modulations during singing. It should be noted that these indings should be interpreted cautiously, as they are confounded with the fact that older children may have better ability to both remember and produce learned songs. As well, older children many have chosen more dificult songs to sing. Furthermore, there was considerable variability in performance across individual children. Mizener (1993) used trained raters and a 7-point scale to assess the degree of tonality in children’s singing of familiar songs (“Begins and ends in same tonality, with no loss of tonality within the song and no noticeably inaccurate intervals = 7… has no clearly established tonal center and most intervals are inaccurate, or is chanted in spoken tones = 1”, p. 235). It was found that children in Grades 4 and 5 sang with better subjective tonality than children in Grades 3 and 6. Again, these indings should be interpreted cautiously, as the measure of tonality was subjective and there was no control for cognitive factors such as memory or prior music training, both of which may relate to improved singing performance. In sum, assessments of tonality in children’s singing generally show improvements with age, but these improvements appear to be neither perfectly progressive nor consistent across contexts. However, the lack of control measures and objective assessments of tonality and pitch accuracy make it dificult to interpret these indings. The sensorimotor loop model of singing would suggest that perceptual knowledge of musical key and harmony needs to become integrated with motor proiciency in order for good singing to develop. In this regard, more data are needed on the relationship between perception and performance, and the effects of experience and formal instruction. s i n g i n g ac c u r ac y a n d c o g n i t i v e l oa d : i n t e r ac t i o n s b e t w e e n m u s i c a n d l a n g uag e Inconsistencies across studies, puzzling reports of lack of consistent improvement with age, and the difference between self-chosen and learned songs all suggest that extra-musical factors inluence singing production. General cognitive skills, such as memory, likely have a large impact on the quality of children’s singing productions and have a long timeline for development (e.g., Case, Kurland, & Goldberg, 1982; Siegel, 1994), such that they continue to develop well into middle-childhood. For example, virtually all verbal measures of memory show improvement from preschool years into adolescence (see Gathercole, Pickering, Ambridge, & Wearing, 2004 for a review). Reducing cognitive load has been found to enhance singing proiciency even in adults. Berkowska and Dalla Bella (2009b) found that novice or occasional adult singers showed improved singing performance when linguistic demands were reduced. This effect is also found in the developmental literature. Children in kindergarten, irst grade, and third grade have been found to have better pitch accuracy when singing without song lyrics on the neutral syllable /loo/ than when singing with lyrics (Goetze, 1985/1986 as cited by Welch, 2006). Yarbrough et al. (1991) also found that kindergarten children performed best using the syllable “la” rather than using the syllables “sol-mi” which matched the interval (descending minor third) sung by the model. However, the presence of lyrics does not necessarily cause poor singing. In contrast to Goetze (1985/1986 as cited by Welch, 2006), children in Grades 1 to 3 were judged as more accurate when singing songs with original words than when singing songs on the syllable /loo/ (Hanna, 1999). Other studies have also found no signiicant differences in pitch-matching accuracy between preschoolers who sang with or without words (Sims, Moore, & Kuhn, 1982), and kindergarten and Grade 1 children performed equally well when singing songs with complete lyrics, strings of words, or no words (Levinowitz, 1989). These inconsistencies across studies may relate to the fact that the length 37 Christine D. Tsang, Rayna H. Friendly, & Laurel J. Trainor of the song and degree of familiarity of the song also affect cognitive load and therefore may affect children’s singing performance. In general, when the cognitive load is high, young children appear to pay more attention to the words than to the melody (Guerrini, 2006). Preschool children show a bias towards learning the words of songs, which is not matched by an ability to learn and accurately reproduce the melodic components of those songs (Levinowitz, 1989). Five- to seven-year-old children are also more accurate in reproducing the words of a song than the pitches within the same song taught to them by their music teacher (Welch et al., 1998). Furthermore, boys have been found to be less accurate when singing with lyrics than girls (Welch, 2000), a inding that parallels the linguistic advantage that is often shown in preschoolers’ language acquisition for females over males (e.g., Huttenlocher, Haight, Bryk, Seltzer, & Lyons, 1991). In sum, whether or not the sensorimotor loop can be eficiently employed to produce accurate singing depends on the cognitive load. Given general improvements in cognitive skills such as memory and attention over time, it is important to separate development of the sensorimotor loop itself from the development of general cognitive skills when assessing singing development. m e c h a n i s m s d r i v i n g i m p rov e m e n t s i n s i n g i n g : t h e ro l e o f e x p e r i e n c e a n d s e n s o r i m o t o r i n t e r ac t i o n s According to Welch, Howard, and Rush (1989), increasing competency in singing is related to two main factors: 1) maturation, including basic physiological maturation of the vocalmotor apparatus and brain development, and 2) experience with music and sound, in the form of vocal models and vocal practice. The role of experience and training in singing is the focus of much of the music education literature. Several studies of adolescent instrumental musicians have shown that pitch accuracy is signiicantly related to amount of music training, such that the number of years of music training predicts tuning accuracy when playing their instrument 38 (Geringer & Witt, 1985; Yarbrough, Karrick, & Morrison, 1995; Yarbrough, Morrison, & Karrick, 1997). Interestingly, none of these studies, nor several other studies (e.g., Apfelstadt, 1984; Bradshaw & McHenry, 2005; Geringer, 1983), found a signiicant relationship between pitch discrimination and accuracy of pitch production. However, same-different discrimination, the chief perceptual task in the majority of these studies, is often an unreliable measure of perceptual ability in young children because of biases to say either “same” much of the time or to say “different” much of the time (e.g., Marsh, 1986). In terms of singing, several studies using matched perception and production measures in both adults and adolescents have found a signiicant positive relationship between pitch-matching accuracy and melodic perceptual abilities (e.g., Demorest, 2001; Demorest & Clements, 2007; Phillips & Aitchison, 1997). This result suggests that good pitch perception contributes to accurate pitch singing. However, in the case of adults with poor singing ability, there is often a dissociation between pitch perception and motor skill (e.g., Dalla Bella et al., 2007; Loui, Guenther, Mathys, & Schlaug, 2008; Pfordesher & Brown, 2007), such that some adults can perceive pitch accurately but not produce it accurately or vice versa. While there are a few studies in the music education literature showing small correlations between singing pitch accuracy and pitch perception abilities (e.g., Demorest, 2001; Demorest & Clements, 2007; Rutkowski, 1996), there are no studies directly examining children’s singing production and perception abilities, making it dificult to determine the role of sensorimotor integration in the development of singing accuracy. According to the vocal sensorimotor loop model, vocal motor production during singing is mediated by perceptual feedback, which requires a comparison between an “internalized voice” used to plan and predict motor instructions for vocal output and feedback from sensory information that monitors the actual output. The internalized voice is thus a key component of singing proiciency. Participants self-categorized as tone deaf may lack a well-developed internalized voice, which is Singing development consistent with the inding that pitch-matching accuracy can be improved when singing along with the pattern to be imitated, as in choral singing (Wise & Sloboda, 2008), a inding also reported by Pfordesher and Brown (2007) in highly proicient singers. These results support the idea that the perceptual feedback loop plays a critical role in singing development. Evidence from voice modeling studies also supports this idea. Moore, Estis, Gordon-Hickey, and Watts (2008) found that adult pitch-matching performance is best when matching to the timbre of one’s own voice, rather than to a neutral female voice or to non-vocal complex tones, a inding which suggests that singers are comparing the model to an internalized voice that sounds like their own voice, and feedback that best matches the internalized model results in better singing. The notion that singers compare an internalized melodic model to external auditory feedback is also supported by the inding that singers receiving altered feedback sang different notes compared to trials in which feedback was unaltered (Jones & Keough, 2008), again suggesting that auditory feedback is a critical aspect of singing proiciency. Research examining the effect of voice model characteristics on children’s pitch-matching accuracy are less clear, with some studies showing that children show higher accuracy rates when imitating female voices (Yarbrough et al., 1991), other studies indicating that child voice models enhance singing accuracy (Green, 1990; Petzold, 1969) and still others showing no effect of voice model (Small & McCachern, 1983). However, it does appear that, in general, the more similar the voice model to the child’s voice, with respect to range, quality, and timbre, the better the child’s singing accuracy. Together, these indings suggest that the development of an internalized vocal model may occur gradually over time, and may be affected by improving cognitive abilities (to deal with the memory and cognitive demands of the modeling task) and increasing musical experience (both perceptual and productive). Interestingly, Jones and Keough (2008) also found that highly trained adult singers were much more susceptible to shifts of the internal model based on erroneous external feedback than non-trained singers, possibly indicating that music experience may enhance reliance on the internal model. Zarate and Zatorre (2008) found that experienced singers were better able to maintain singing accuracy and consistency in the presence of pitch-shifted feedback, compared to non-musicians, providing further support for the idea that training can enhance sensitivity to auditory feedback. Coupling auditory feedback with visual displays has also been found to enhance children’s singing accuracy, supporting the role of external environmental feedback in singing development. For example, Siebenaler (1999) found that visual feedback (where a ruler was used to visually represent the relationship between children’s sung pitch and the correct pitch) was more effective than either physical feedback (where children’s hands were moved to physically represent this relationship) or verbal feedback alone in facilitating pitchmatching accuracy for children in kindergarten and Grade 1. Similarly, real-time computerized visual feedback was found to be signiicantly better at improving children’s pitch-matching skills compared to traditional techniques where children sang in a group accompanied by an adult playing guitar (Welch et al., 1989). In sum, the vocal sensorimotor loop model of singing implies a complex relationship between the perceptual and motor systems in the context of internal and external feedback, and these complex relations take time to develop and are greatly inluenced by experience, practice, and cognitive skills. c o n c lu s i o n s In this paper, we examined empirical studies on singing development with respect to the vocal sensorimotor loop model described by Berkowska and Dalla Bella (2009a). While the evidence is generally consistent with a complex process involving perception, production, cognition and environmental feedback, the complex interplay between these components during development remains largely unknown. Further understanding of the development of good singing will come from 39 Christine D. Tsang, Rayna H. Friendly, & Laurel J. Trainor studies that address relations between perception and performance, and examine the roles of age, musical training and experience, and general cognitive skills in the context of the development of sensorimotor interactions. Understanding the mechanisms that underlie the development of good singing can potentially enable the creation of optimal educational programs for singing and early musical engagement. r efer ences Amir, O., Amir, N., & Kishon-Rabin, L. (2003). The effect of superior auditory skills on vocal accuracy. Journal of the Acoustical Society of America, 113, 1102-1108. Apfelstadt, H. (1984). Effects of melodic perception instruction on pitch discrimination and vocal accuracy of kindergarten children. Journal of Research in Music Education, 32, 15-24. Bentley, A. (1969). Monotones. Music education research papers. London: Novello and Company. Berkowska, M., & Dalla Bella, S. (2009a). Acquired and congenital disorders of sung performance: A review. 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Neuroimage, 40, 1871-1887. au t h o r n o t e s This work was funded by the Social Sciences and Humanities Research Council of Canada (SSHRC) Major Collaborative Research Initiative Program (MCRI) research initiative, Advancing Interdisciplinary Research in Singing (AIRS). We thank Andrea Unrau and Robin Eles for comments on an earlier version of this manuscript. 43 Christine D. Tsang, Rayna H. Friendly, & Laurel J. Trainor biogr aphies Christine Tsang is an Associate Professor and Chair of the Department of Psychology at Huron University College at the University of Western Ontario. She has published several research articles on the development of music Christine Tsang perception during infancy. Her many research interests include examining the effect of context on infant musical preferences, multimodal perception of music during infancy, and the role of music training on language and cognitive development. Christine is also a classically trained pianist, and in recent years has started playing the violin. Rayna Friendly is a PhD candidate from McMaster University’s department of Psychology, Neuroscience and Behaviour in Hamilton, Ontario. As a member of the Infant Auditory Lab, Rayna works under the supervision of Dr. Rayna Friendly Laurel Trainor: a leading researcher in the ield of auditory development and music cognition and perception. Rayna has been singing in school choirs and small ensembles for over 10 years and is currently a member of McMaster University’s Vocal Ensemble. In her research, Rayna has expanded on her interest of the voice and singing, by studying the development of voice discrimination during the irst year of infancy, as well as the development of singing abilities in young children. Rayna’s research in singing has been supported by the Advancing Interdisciplinary Research in Singing (AIRS) initiative, where she has taken on many leadership roles such as Co-ordinator of the annual AIRS Student 44 and Professional Meeting, and primary editor of the AIRS Student and Professional Newsletter. Rayna loves working in a ield that allows her to combine her interests in psychology and music and looks forward to future related endeavors. Laurel Trainor is a Professor in the Department of Psychology, Neuroscience and Behaviour at McMaster University, a Research Scientist at the Rotman Research Institute at Baycrest Hospital, Toronto. She is the Founding Director of the Laurel Trainor McMaster Institute for Music and the Mind, a multidisciplinary group of researchers whose mandate is to promote the scientiic study of music, to promote music education, and to engage the community. This group has recently received a grant from the Canada Foundation for Innovation and partners to build cutting edge laboratories to study music performance and performer-audience interactions. She has published over 100 research articles and book chapters on the neuroscience of auditory development and the perception of music in journals including Science, Nature, Journal of Neuroscience, Signal Processing and Psychological Science. She is a fellow of the Association for Psychological Science, and an Innovator of Distinction. She has given invited keynote addresses at many major academic conferences and her research has a high media proile. In addition, she holds major grants from the Canadian Institutes of Health Research, the Natural Science and Engineering Research Council of Canada, the Social Science Research Council of Canada, and the Grammy Foundation. Laurel also has a Bachelor of Music Performance from the University of Toronto, likes playing chamber music, and is currently principal lute of Symphony Hamilton. À