- Kenya airport whistleblower fears for his life
- Sheinbaum to take office as Mexico's first woman president
- Scientists fear underfunded Argentina research on verge of collapse
- US port officials gird for strike despite last-minute bargaining
- With 118 dead from Hurricane Helene, Biden defends US government response
- Breeder who tried to create enormous trophy sheep jailed in US
- Qatar Airways seeking 25% stake in Virgin Australia
- US port officials gird for strike as labor talks stay stuck
- As toll crosses 100, Trump puts Hurricane Helene at election center stage
- US Fed Chair sees 'further disinflation' in economy
- Epic Games sues Google and Samsung over app store
- Officials see no shortages from likely US port strike
- UK families of Gaza hostages warn Lebanon attack 'takes focus away'
- Shares in Stellantis, Aston Martin skid on profit warnings
- Dali prints found in London garage sold at auction
- ECB chief backs bank mergers amid UniCredit, Commerzbank talk
- China stocks soar on stimulus, but US and Europe retreat
- 100 dead in storm Helene damage, flooding across US southeast
- China stocks soar on stimulus, Europe slides on automaker woes
- German antitrust watchdog steps up monitoring of Microsoft
- Nepal's urban poor count cost of 'nightmare' floods
- E.Guinea, Gabon clash at ICJ over oil-rich islands
- New blow for UK's Starmer as growth data disappoints
- China's top banks to tweak mortgage rates to boost housing market
- Muslim women break taboos navigating east London's waterways
- Nepal dam-building spree powers electric vehicle boom
- More than 60 dead from storm Helene as rescue, cleanup efforts grow
- Dozens missing, 9 dead in migrant boat wreck off Spanish Canaries
- Death toll from Hurricane John hits eight in Mexico
- Storm Helene's toll rises as rescue and cleanup efforts gain pace
- SpaceX launches mission to return stranded astronauts
- Storm Helene kills 44, threatens more 'catastrophic' flooding as cleanup begins
- SpaceX set to launch mission to return stranded astronauts
- Storm Helene kills 44, threatens more 'catastrophic' flooding
- Boeing strike grinds on as latest talks fail to reach agreement
- Iran 'news' sites, hackers target Trump ahead of US election
- US ports brace for potential dockworkers strike
- Japan's speedy, spotless Shinkansen bullet trains turn 60
- US hurricane deaths rise to 44, fears of more 'catastrophic' flooding
- Global stocks mostly rise, cheering Beijing stimulus
- Europe en route for Moon with new simulator, says astronaut Pesquet
- Fireworks forecast if comet survives risky Sun flypast
- Argentina judge orders dictionary to delete pejorative definition of 'Jewish'
- Global stocks rise on rate hopes, Beijing stimulus
- S.African woman turns 118, among the oldest in the world
- UK clears $4 bn AI partnership between Amazon, Anthropic
- Barca fans barred from Champions League away game over racist banner
- Chinese stocks extend surge, Europe higher on Beijing stimulus
- Pope says Church must 'seek forgiveness' for child sexual abuse
- China caps week of 'bazooka' stimulus for ailing economy with rate cut
A whiff of tears reduces male aggression, says study
Watching someone cry often evokes an emotional response -- but according to a new study published Thursday, human tears themselves contain a chemical signal that reduces brain activity linked to aggression.
The research was carried out by the Weizmann Institute of Science, Israel, and appeared in PLOS Biology, a US science journal. Though it involved female tears, because women made themselves available as donors, it probably isn't a sex-dependent effect, the authors say.
Numerous studies have shown rodent tears contain chemicals serving as social signals they emit on demand -- female mice tears for example reduce fighting among males; and subordinate male mole rats smear themselves in their own tears so that dominant males attack them less.
To find out whether similar effects occurred in humans, a team led by PhD student Shani Agron first exposed 25 male volunteers to either "emotional" tears, or to saline. The volunteers couldn't tell what they were sniffing as both substances are clear and odorless.
The tears were obtained from six female volunteers who watched sad films in isolation and used a mirror to capture the liquid in a vial as it trickled down their cheeks.
"When we looked for volunteers who could donate tears, we found mostly women, because for them it's much more socially acceptable to cry," said Agron in a statement.
She added that since prior research had shown tears reduce testosterone levels in men, and that lowering testosterone has a greater effect on aggression in men than in women, "we began by studying the impact of tears on men because this gave us higher chances of seeing an effect."
They had the volunteers play a computer game that had been well established in prior aggression studies, and involves accumulating money while a fictitious opponent could steal their earnings.
Given the opportunity, the men could get revenge on the other player by causing them to lose money, even though in their own case they would not gain from the opponent's loss.
Such revenge-seeking, aggressive behavior in the game dropped 43.7 percent after men sniffed the tears.
This appeared to mirror what had been observed in rodents, but unlike rodents, humans don't have a structure in their noses called a vomeronasal organ, which was lost during our species' evolution and detects odorless chemical signals.
To find out what was going on, the researchers applied the tears to 62 olfactory receptors in a lab dish and found that four receptors were activated by tears, but not saline.
Finally, the scientists repeated the experiments with the men's brains connected to MRI scanners.
The imaging revealed the prefrontal cortex and anterior insula, which are related to aggression, became more active when men were provoked during the game, but the effect was not as strong if they had sniffed tears.
"We note that crying often occurs in very close-range interactions, to the extent that 'kissing teary cheeks' is a recurring theme across cultures," wrote the authors, adding that emitting chemical signals to prevent aggression was probably even more important among infants, where verbal communication isn't possible.
Y.Jeong--CPN