The next time you whisper sweet nothings in someone’s ear, you might want to target their left side.
Neuroscientists from the Federal Polytechnic School of Lausanne (EPFL), Lausanne University Hospitals and the University of Lausanne in Switzerland discovered a strange bias in our perception of pleasant voices.
According to brain scans of 13 adults, positive human sounds, such as laughter, trigger stronger neural activity in the brain’s auditory system when heard from the left side, suggesting that the human auditory cortex is specially adapted to the direction of the sounds that make us happy.
It is unclear why there is a preference – tThe experiments focused only on activity changes in the auditory cortex. How such a change translates to someone’s perception of these sounds is unknown and should be tested in future research.
That said, previous studies showed that the left ear can more easily identify the emotional tone of someone’s voice, hinting at an underlying specialization.
Since the left ear first transmits information to the right hemisphere of the auditory cortex, it has been speculated that the right side of the brain must process emotions better than the left side.
But these recent findings suggest that may not be the right answer.
When study participants listened to happy human vocalizations from three different directions — either left, center, or right — both sides of their auditory cortex activated.
Recordings heard only from the left side, however, elicited a much stronger neurological response.
“It doesn’t happen when positive vocalizations come from the front or the right,” said neuroscientist Sandra da Costa from EPFL.
“We also show that vocalizations with neutral or negative emotional valence, for example meaningless vowels or frightened cries, and sounds other than human vocalizations do not have this association with the left side.”
The direction of a noise can obviously impact the quality of that sound – think of an ambulance siren moving towards you and then away. And it can also have an impact on our perception.
Previous studies showed that imminent sounds are often perceived as more disturbing and exciting than distant sounds. And the proof suggests a person is more easily aroused when a sound comes from behind.
Increased sensitivity to certain noises from certain directions has a broad evolutionary meaning. Survival of a human over millennia past would undoubtedly have depended on an additional distrust of sounds sneaking up from behind.
But a left-handed bias for emotion in human voices isn’t so easily explained.
Some brain functions are known to reside more on the left side of the brain than the right side, and vice versa, but in this particular case, that doesn’t seem to explain the results.
While the right hemisphere of the auditory cortex showed a stronger response to happy human voices in a region called L3, both sides of the brain were activated by sounds during experiences.
“It is currently unknown when the preference of the primary auditory cortex for left-positive human vocalizations arises during human development, and whether it is a uniquely human characteristic,” he added. said neuroscientist Stephanie Clarke.
“Once we understand this, we can speculate whether it’s related to hand preference or asymmetrical arrangements of internal organs.”
The study was published in Frontiers in Neuroscience.