Research results that laughter and sweet whispers cause a stronger reaction in the brain when heard from the ``left side''

In everyday life, you may not care whether the person you are talking to is on your right or left side. However, a Swiss research team published in the peer-reviewed journal Frontiers in Neuroscience found that positive vocalizations, such as laughter and erotic voices, are more likely to be heard in the brain when they come from the left side of the body. It is said to provoke a strong reaction.

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Sounds generated in this world are defined by their frequency and amplitude, but for humans, sounds have meanings that go beyond mere parameters. You must to do something before you go on. Past studies have shown that humans perceive sounds approaching them as more dangerous and exciting than sounds moving away, and that they are more sensitive to sounds heard from behind.

A bias towards sounds coming close to you or behind you is thought to have an evolutionary advantage. For our ancestors who lived in the wild, sounds approaching from behind could be a sign of a predator, and sensitivity to such sounds could have been important for survival. .

Newly, a research team at the Swiss Federal Institute of Technology Lausanne and the University of Lausanne conducted an experiment to investigate whether the brain's reaction changes depending on the direction in which the sound was heard.

The research team used

magnetic resonance imaging (fMRI) to measure the brain activity of 13 volunteers and investigated how strongly the brain reacts to sounds heard from the left, front, and right. All of the subjects were men and women in their twenties, all were right-handed, and none had received musical training.

Subjects included 'positive human voices' ranging from erotic to laughter, 'neutral human voices' with meaningless vowels or consonants, 'negative human voices' including screams and fights, and applause. 'Non-human positive sounds' such as the sound of opening a beer can or the sound of opening a beer can, 'Non-human neutral sounds' such as the sound of a car engine or wind, and 'Non-human sounds' such as the sound of a time bomb exploding or the sound of breaking glass. He listened to sounds classified into six types, 'negative sounds', and measured the brain's reaction to them.

Focusing on the primary auditory cortex in both hemispheres of the brain, the area called L3 in the right hemisphere responded more strongly to ``positive human voices,'' but was similarly activated to the sounds heard as a whole. Did. However, it has been reported that the primary auditory cortex in both hemispheres was most activated when ``a positive human voice was heard from the left''.

Senior author Sandra da Costa, Ph.D., of the Swiss Federal Institute of Technology in Lausanne, said: 'This study shows that when voices that evoke positive emotional experiences come from the listener's left side, they produce stronger activity in the auditory cortex of the brain. This response does not occur when positive voices are heard from the front or from the right.' 'Also, voices with neutral or negative emotions and sounds other than human voices are heard from the left.' It has also been shown that there is no relationship between

'Positive emotional voices coming from the left strongly activate the primary auditory cortex of the brain hemisphere, the cerebrum that first receives auditory information,' says co-author Tiffany Grizendi, a doctoral student at the University of Lausanne. 'It's a cortical region. Our findings suggest that the emotional nature and spatial origin of sound are first identified and processed there.'

The study did not clarify why the brain responds more strongly to positive voices coming from the left side. Co-author Stephanie Clarke of the University of Lausanne said: 'When in human development does the primary auditory cortex prefer positive voices coming from the left, or is this a unique human trait? If we know this, we may be able to infer whether it is related to the dominant hand or the asymmetrical placement of internal organs.'

in Science, Posted by log1h_ik