The next time you whisper sweet nothings into someone’s ear, you might want to aim for their left side.
Neuroscientists from the Swiss Federal Institute of Technology in Lausanne (EPFL), the University Hospital of Lausanne and University of Lausanne in Switzerland have discovered a strange bias in our perception of pleasant voices.
According to brain scans of 13 adults, positive human sounds, such as laughter, elicit stronger neural activity in the brain’s auditory system when heard on the left side, suggesting that the human auditory cortex is specifically tuned to the direction of sounds that make us happy.
It is not clear why there is a preference at all – the experiment focused only on changes in activity in the auditory cortex. How such a change translates into one’s perception of these sounds is unknown and needs to be tested in future research.
that said previous studies showed that the left ear can more easily identify the emotional tone in someone’s voice, hinting at some hidden specialization.
Since the left ear feeds information first to the right hemisphere of the auditory cortex, it is assumed that the right side of the brain should be better at processing emotions than the left side.
But these recent results suggest that may not be the right answer.
When study participants listened to happy human vocalizations from three different directions—left, center, or right—both sides of their auditory cortex were activated.
Recordings heard only on the left side, however, elicited a much stronger neurological response.
“This does not happen when positive vocalizations come from the front or right,” says neuroscientist Sandra da Costa from EPFL.
“We also show that vocalizations with neutral or negative emotional valence, such as nonsense vowels or frightened screams, and sounds other than human vocalizations do not have this association with the left side.”
The direction of the noise can obviously affect the quality of that sound – think of an ambulance siren as it travels towards you and then moves away. And it can also affect our perception.
Previous studies have shown that approaching sounds are often perceived as more sinister and arousing than receding sounds. And evidence assumes one gets excited more easily when a sound comes from behind.
Increased sensitivity to certain noises coming from certain directions makes broad evolutionary sense. Man’s survival in past millennia undoubtedly depended on being particularly suspicious of sounds that crept up from behind.
But the left-handed bias for emotion in human voices is not so easily explained.
Certain brain functions are known to reside more in the left side of the brain than in the right, and vice versa, but in this particular case this did not seem to explain the results.
While the right hemisphere of the auditory cortex showed a stronger response to happy human voices in one area called L3, both sides of the brain were activated by the sounds in the experiments.
“It is currently unknown when the preference of the primary auditory cortex for left-sided positive human vocalizations emerges during human development and whether it is a uniquely human characteristic,” says neurologist Stephanie Clarke.
“Once we understand this, we can speculate whether it is related to hand preferences or to asymmetric arrangements of internal organs.”
The study was published in Frontiers in Neuroscience.
Leave a Reply