'Beat Deafness' – A New Form of Amusia

Illustration of three people wearing headphones and dancing to music.
Written by Melissa Wong
Illustrated by Tammy Lee
Have you ever found yourself fully immersed in a song, bopping your head to the music, only to have someone tell you that your movements are completely out of sync? Or has a friend asked you for feedback on a song they recorded and you think they sound amazing, but your other friend sitting beside you is cringing at how out-of-tune the singing is? The inability to synchronize to a song’s pulse–beat deafness–or to recognize changes in pitch–tone deafness–are both forms of a musical disorder called amusia. People born with this condition have what is known as congenital amusia.

For a long time, amusia was characterized by pitch deafness. However, beat deafness was recently identified as another form of amusia. Beat deafness is very rare and affects approximately three percent of the population, whereas pitch deafness affects approximately five percent of the population. As well, half the individuals identified with pitch deafness also have beat deafness; the literature reports some correlation between the two forms of amusia.

The process of detecting a beat is thought to involve the brain’s ability to predict the beat, as well as the brain’s internal beat-keeping mechanism. However, this process is impaired in individuals with beat deafness, resulting in their inability to synchronize to the beat when listening to external sounds such as music. In a study conducted at the University of Montreal, two individuals diagnosed with beat deafness were able to keep a steady beat in the absence of external sounds. However, compared to people unaffected by beat deafness, the two individuals took a much longer time to adjust their tapping in response to a tempo change produced by an external sound (e.g. a metronome).

There also seems to be a connection between beats and motor functioning. The synchronization to external beats allows for coordinated movements, like dancing to your favourite song. This might explain why someone who is beat-deaf would dance out of sync with the song. Likewise, listening to a slow ballad may not be your first choice of music for a high-intensity workout. For those of us who can detect beats normally, the tempo and beat of a ballad clearly do not fit with the intense workout!

Ultimately, beat deafness is characterized by the asynchronization between the pulse of an external sound and the motor response to the beat. This recent discovery not only demonstrates the role of beats in coordination, but may also explain why we choose to listen to certain types of music for different tasks! In terms of music, amusia highlights the importance of both the beat and the melody. The two musical elements are processed in the brain, and impairment to the processing of either element will lead to amusia.

Sources:

  1. https://www.health.harvard.edu/newsletter_article/Music_to_their_ears_it_is_not
  2. https://doi.org/10.1016/j.cortex.2018.11.036
  3. https://doi-org.myaccess.library.utoronto.ca/10.3389/fnins.2016.00040
  4. https://www.youtube.com/v/sVYsoXat2pw?version=3&hl=en_US&rel=0
  5. https://www.mcgill.ca/channels/news/so-you-think-you-can-clap-beat-239990
  6. https://www.nature.com/articles/s41598-020-65034-9#Abs1