Laughter is great medicine — when you hear it from your left side, brain study reveals

LAUSANNE, Switzerland — The way we perceive sounds goes beyond their physical characteristics. They can also evoke emotions and convey meaning. Now, it turns out that which ear we hear sounds in can have a significant impact on our well-being. Researchers have discovered that the direction from which sounds can influence our emotional response — with sounds from the left side provoking stronger emotions.

Looming sounds approaching from behind may trigger negative emotions, possibly due to our evolutionary instincts to perceive them as potential threats. However, the new study, from neuroscientists in Switzerland, reveals that positive human sounds, like laughter, have a stronger impact when they come from the left.

“Human vocalizations that elicit positive emotional experiences show strong activity in the brain’s auditory cortex when they come from the listener’s left side,” says Dr. Sandra da Costa, a research staff scientist at the Swiss Federal Institute of Technology in Lausanne. “This response does not occur when positive vocalizations come from the front or right side. However, sounds with neutral or negative emotional valence, such as meaningless vowels or frightened screams, do not show this association with the left side.”

People laughing together
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To investigate this further, the researchers conducted brain imaging scans on 13 volunteers while they listened to sounds from different directions. They observed that regions of the brain involved in early sound processing, such as the primary auditory areas A1 and R, exhibited maximum activation when positive vocalizations came from the left. In contrast, responses were diminished when the same sounds came from the front or right, or when participants heard neutral or negative vocalizations and non-vocal sounds.

“The strong activation by vocalizations with positive emotional valence coming from the left occurs in the primary auditory cortex of either hemisphere, which are the first areas in the brain to receive auditory information,” adds study co-author Dr. Tiffany Grisendi in a media release. “This suggests that the emotional valence and spatial origin of a sound are first processed in these areas.”

Interestingly, the response in area L3 of the right hemisphere was also heightened when positive vocalizations came from the left or right compared to the front. However, this asymmetry did not affect the response to non-vocal sounds.

The researchers are still uncertain about the evolutionary significance of the brain’s bias towards positive vocalizations from the left. Professor Stephanie Clarke, a senior author of the study, suggests that further investigation is necessary to determine when this preference develops in humans and whether it is linked to hand preference or the asymmetric arrangement of internal organs.

The study is published in the journal Frontiers in Neuroscience.

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