The human brain's perception of sounds extends beyond its frequency and amplitude. Sounds can evoke various meanings and emotions, ranging from pleasantness or unpleasantness to being ominous or reassuring. They can also be perceived as interesting and informative or simply noise.
In a recent study, titled "Emotional Sounds in Space: Asymmetrical Representation Within Early-Stage Auditory Areas" published in Frontiers in Neuroscience, neuroscientists from the Swiss Federal Institute of Technology Lausanne (EPFL), Lausanne University Hospital, and the University of Lausanne in Switzerland have uncovered an intriguing bias in how people perceive pleasing voices.
Human Auditory Cortex More Tuned to Happy Sounds
When it comes to whispering sweet-nothings, the researchers found that targeting the left side of a listener's ear has a peculiar effect on their perception of voices.
Brain scans of 13 adults have revealed that positive human sounds, such as laughter, elicit stronger neural activity in the auditory system when heard from the left side. According to Science Alert, this suggests that the human auditory cortex is specifically attuned to the direction of sounds that evoke happiness.
The underlying reasons for this preference remain unclear as the experiments focused solely on changes in activity in the auditory cortex. Further research would be needed to understand how such changes in neural activity translate into the perception of these sounds.
Previous studies have indicated that the left ear is better at discerning the emotional tone in someone's voice, suggesting a potential specialization. It was previously believed that the right hemisphere of the auditory cortex, which receives information from the left ear, was superior in processing emotions. However, the recent findings challenge this assumption.
Both sides of the auditory cortex were activated when participants listened to happy vocalizations from different directions, but neuroscientist Sandra da Costa said recordings heard exclusively on the left side produced a significantly stronger neurological response. This effect was not observed when positive vocalizations came from the front or right side, indicating a specific association with the left side.
The direction of a sound can impact its quality and our perception. Looming sounds, for example, are often perceived as more ominous and arousing than receding sounds. The research suggests that heightened sensitivity to certain sounds from specific directions may have had evolutionary advantages, enabling humans to be more alert to potential threats approaching from behind.
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Left-Handed Bias Baffles Scientists
The findings of the study left scientists baffled because the left-handed bias in perceiving emotion in human voices is not easily accounted for. Although certain brain functions are typically associated with either the left or right side of the brain, this does not seem to explain the observed results in this case.
While the right hemisphere of the auditory cortex showed a higher reaction to cheerful human voices in a particular area called L3, the sounds affected both sides of the brain during the studies.
The precise timing of when the preference for positive human vocalizations from the left side emerges in human development, as well as whether this characteristic is unique to humans, remains unknown.
Neuroscientist Stephanie Clarke highlights in the news release the need to understand this aspect to speculate on potential connections with hand preference or the asymmetric arrangement of internal organs. More study is needed to shed light on these issues.
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