Listening to filtered music improves social communication among children with autism

Based on the melodic range of mothers, the adapted music soothes hypervigilant physiologies and signals the middle ear to tune into the human voice.

Listening regularly to specially adapted music helps children with autism comprehend voices and communicate better by reducing their hypersensitivity to background noise, according to our research.

These findings offer potential treatments for people with autism spectrum disorder (ASD) that could allow them to participate more fully in social life. We found that exposure to this music for 45 minutes daily over five days altered the operation of the middle ear so that it filtered out more of the low-frequency sounds that dominate the acoustic spectrum in our mechanized society (such as ventilation systems, traffic, airplanes, vacuum cleaners and other appliances). In people with ASD, hypersensitivity to these low frequencies can prevent the higher frequencies of human speech from reaching the brain, hindering social communication.

“Hypersensitivity to low frequencies in people with autistic spectrum disorder can prevent the higher frequencies of human speech from reaching the brain. This process gets in the way of social communication.”

Nervous system important in ASD

Our research also indicates how this reduced sensitivity occurs and demonstrates that the human nervous system is important in ASD. It suggests that particular forms of music alter the physiology of individuals with ASD and, as a result, reduce their tendency to over-anticipate danger. Listening to the music changes the rhythm of the heart. This change in heart rhythm is linked to signals via the nervous system that reduce hypervigilance. This altered, more relaxed, physiological state sends messages to the neural circuit regulating the middle ear muscles, which then function more normally rather than in a hypervigilant mode. As a result, the auditory system can process human speech more effectively. A shift toward a calmer physiology also leads the person with ASD to more social behaviors, such as sharing, that are characteristic of diminished reactivity to danger cues.

The ‘social engagement system’

In short, the music we used in the experiment affects the “social engagement system” —nerves that help regulate the muscles of the head, face, and heart. These nerves control muscles of ingestion and eating, and they help the middle ear dampen background sound so that we can hear even soft voices. This system also controls muscles of the face and head that let us express emotions and alter the intonation of our voices.

In several clinical populations such as autistic children, hypersensitivity to sounds tends to coincide with difficulty regulating behavior. Autistic children often have poor muscle tone in the upper part of the face; they have flat facial expressions and speak in a monotone with limited prosody (i.e., the intonation of voice that conveys emotion). They modulate their voices not by altering frequency or pitch but by speaking more loudly. It is clear that children with ASD have a compromised social engagement system, which is linked to their physiological state. Listening to vocal music that is characterized by large shifts in intonation triggers the social engagement system and helps children shift to a calm physiological state.

Music influences physiology

The computer-altered music we used in our trials is based on the frequency range of the female voice, so it functions much like a mother singing a lullaby to a child. The altered music removes all low-pitch frequencies, because low frequency sounds can signal a threat to life. All high-pitched sounds were also removed, because high frequency sounds can signal danger as well. Through experiments with hundreds of children, we’ve found that this form of amplified prosody altered the subjects’ physiological state and dampened auditory hypersensitivity.

Our growing understanding about how low-frequency sounds get in the way of the higher frequencies of human speech should help in designing public environments, notably clinical, educational, and healthcare environments. Most architecture for work spaces is based on optimizing efficiency, cleanliness, and ability to monitor. There is little emphasis on making sure that low-frequency sounds do not dominate.

There is also little understanding that people respond to acoustic stimuli in different ways, depending on their physiological state. So the physiological state of people with autism, combined with environments that resound with low frequencies, means that they find it much more difficult to process words that, to other people, might seem simple to understand and evaluate. The challenge in treating people with ASD is to work out how to influence their physiological state and also create more conducive environments for them to develop their social communication.Policy makers need to provide environments that appreciate the individual differences in sensitivity to physical features.  Classroom design needs to remove low frequency sounds that disrupt physiological state.  Also, policy makers need to provide opportunities for children to ‘exercise’ the neural circuits through reciprocal play, music, and theater, that will promote the development of a child who is behaviorally resilient.Practitioners need to be aware of the child’s sensitivity to environmental features and the child’s capacity to regulate physiological state. They need to develop an expertise in supporting the child’s behavior through procedures that calm and help regulate the child’s physiological state.  This may be accomplished through supportive gestures, positive facial affect, and warm intonation of voice (i.e., prosody).