The Impact of Musical Experience on Learning Non-native Speech Sounds

Adult non-native speech perception is susceptible to influence from a variety of factors, including those that go beyond the linguistic domain, such as musical experience. Several studies have been interested in the pronounced link between long-term music training and linguistic processing. The aim for the current study is to further investigate this link, and demonstrate the impact of musical experience on the learning of non-native speech sounds, particularly following sleep consolidation. In addition to looking at musical training experience, an objective measure of musical skills including melody, tuning, accent, and tempo was incorporated to allow for more specific analyses of the correlations between various musical skills and language acquisition. Data indicates that there is a significant positive correlation between participants’ phonetic discrimination and performances with melody and tempo assessments following a night’s sleep. This suggests that individuals who are more attuned to melody and tempo parameters of music are better able to demonstrate retention of discrimination of non-native phonetic sounds, particularly following sleep-dependent consolidation. ​THE IMPACT OF MUSICAL EXPERIENCE ON LEARNING NON-NATIVE SPEECH SOUNDS 3 INTRODUCTION Musical training is certainly a rich and versatile experience that has been found to generate positive changes in the brain. In the same manner that physical exercise impacts general body fitness, music acts as “a resource that tones the brain for auditory fitness” (Kraus and Chandrasekaran, 2010). As such, the musician’s brain has been used in several studies as a model for neuroplasticity, suggesting that long-term music training induces certain structural and functional alterations, specifically in the auditory system (Hannon and Trainor, 2007; Musacchia et al., 2007; Kraus and Chandrasekaran, 2010). Findings such as these demonstrate how musicians tend to tune their minds and bodies using cues around them using tactile cues to produce musical notes, using auditory cues to detect pitch, and visuomotor cues to harmonize with the musicians around them. The musician’s brain has functional adaptations for pitch and timbre perception, in addition to structural adaptations for auditory, visual, motor, and cerebellar regions of the brain (Hannon and Trainor, 2007). Due to such functional adaptations, the typical musician’s brain is remarkably different than the typical nonmusician’s brain. For instance, due to the high precision abilities of subcortical centers of the brain to encode acoustic characteristics of sound, researchers were able to demonstrate that musicians, compared to nonmusicians, have more robust auditory brainstem responses to musical stimuli. For instance, exhibited earlier brainstem responses to a speaker saying “da” and a cellist bowing a G note, than did the nonmusician controls (Musacchia et al., 2007). However, as musical training is multisensory in nature, these improved auditory skills that come with musical experience are not exclusively related to music (Magne et al., 2006; Wong et al., 2007; Foregard et al., 2008; Parbery-Clark et al., 2009). For instance, as determined by ​THE IMPACT OF MUSICAL EXPERIENCE ON LEARNING NON-NATIVE SPEECH SOUNDS 4 Foregard et al. (2008), children who received three or more years of instrumental musical training outperformed their control counterparts on two tasks closely related to music, auditory discrimination and fine motor skills, as well as two tasks distantly related to music, vocabulary and nonverbal reasoning skills. As the study of transfer of cognitive performance from one domain to another has been widely examined, it may seem clear why musically trained children are better able to demonstrate a close correspondence between the training domain and the transfer domain, i.e., learning to play a musical instrument and developing fine motor skills and auditory discrimination skills. However, difficulties arise when attempting to demonstrate an instance in which the resemblance between the training domain and the transfer domain is much less obvious, such as learning to play an instrument and understanding mathematical problems (Barnett and Ceci, 2002). Yet, evidence still reports the positive correlation between instrumental musical training and other areas, such as spatial, verbal, and mathematical skills, as well as general IQ (Foregard et al., 2008). Thus, music plays a considerable role in a range of cognitive abilities and overall individual development. Long-term music training can certainly have a positive impact on speech processing, perhaps facilitated by the fact that some cognitive and perceptual processes are shared between music and speech. The processing systems behind both language and music are rather complex, and imply relationships with numerous cognitive abilities, including attention, memory, logic and reasoning, auditory and visual processing, and so on. Both language and music are comprised of several levels of processing. While language is comprised of morphology, phonology, semantics, syntax, and pragmatics, music involves levels of rhythm, melody, and harmony (Besson et al., 2011). Along with this, in both music and speech, the sound sequences ​THE IMPACT OF MUSICAL EXPERIENCE ON LEARNING NON-NATIVE SPEECH SOUNDS 5 involved are hierarchically organized, with speech requiring syllables, words, and sentences, and music involving notes, beats, and phrases. Consequently, there is the potential for a strong similarity between the organization of speech and music from a general standpoint. Furthermore, both speech and musical sounds depend on the same fundamental acoustic parameters, including duration (the length of time of the sound), frequency (how high or low on the musical scale a sound is), intensity (the strength of the sound), and timbre (the pitch and loudness of the sound) (Francois and Schön, 2011). In one study by Intartaglia et al. (2017), subcortical electrophysiological responses to an English syllable [thae] were recorded from three groups of participants: native English speakers, non-native French nonmusicians, and non-native French musicians. Strikingly, the results indicated that subcortical responses to non-native sounds in musicians resembled the neural processing of native speakers, suggesting that long-term musical training may allow one to compensate for the lack of language experience (Intartaglia et al., 2017). As such, researchers have taken quite an interest in the intimate relationship between speech and music, and have examined this relationship from several different perspectives. Several brain imaging studies have investigated the involvement of a working memory with regards to musical tasks (i.e., pressing a button to indicate whether two tones from a sequence presented are the same or different), all demonstrating greater neural activation of the superior temporal gyrus (the primary auditory cortex responsible for processing sound) and longer immediate memory spans in musicians compared to nonmusicians (Tierney et al., 2008; Schulze et al., 2009). In attempts to further account for the differences between musicians and nonmusicians, the Tierney et al. (2008) study used skilled musicians, as well as subjects from comparison groups. The comparison groups included skilled gymnasts to account for another ​THE IMPACT OF MUSICAL EXPERIENCE ON LEARNING NON-NATIVE SPEECH SOUNDS 6 highly structured activity involving repeated practice of specific motor movements, and daily video game players to account for a group that practices a skill daily involving control of fine finger movements and focused attention. By comparing the performance of skilled musicians on a test of verbal memory span to the performance of the two nonmusician groups of gymnasts and video game players, differences in sequence memory between the groups could be measured. Such studies suggest that musicians display longer immediate memory spans than their control groups of nonmusicians, specifically with conditions involving auditory presentation (Tierney et al., 2008). Thus, musicians are able to hold more information, sometimes for longer periods of time, in auditory memory compared to nonmusicians. Similar studies have found that prolonged musical training enhanced selective auditory attention and strengthened working memory (Besson et al., 2011; Strait and Kraus, 2011). For instance, in the Strait and Kraus study, researchers deduced that musicians exhibited strengthened neural networks for selective auditory attention, indicating a potential benefit for individuals who experience a wide range of attention-based language, listening, and learning impairments, by acting as a preventive measure against such impairments and promoting habilitation thereafter. Based on such evidence, it is certainly conceivable that musical training can tune the brain’s executive control network for auditory processing in areas that advance far beyond the musical domain. In addition to the advantages of musical training on memory, recent studies have also investigated the effects of long-term music training associated with advantages that extend to other cognitive abilities, such as linguistic processing. For example, musicians appear to demonstrate stronger neural encoding of speech sounds compared to nonmusicians (Wong et al., 2007; Chandrasekaran et al., 2009; Kraus and Chandrasekaran, 2010). Through the examination ​THE IMPACT OF MUSICAL EXPERIENCE ON LEARNING NON-NATIVE SPEECH SOUNDS 7 of brainstem encoding of linguistic pitch, musicians demonstrate more prominent subcortical activation in response to non-native speech sound stimuli than nonmusicians, implying that long-term musical training can influence basic sensory circuitry. In addition to this, neuropsychological evidence reveals that certain brain regions thought to be language-specific (i.e., the inferior frontal gyrus, Broca’s area) are additi