Many animals are thought to be able to smell fear on humans, but it seems we can sniff out whether other people are spoiling for a fight.
Researchers have found odours in human sweat may alert us if someone is feeling angry or aggressive, helping to put them on alert for potential violence.
Volunteers who sniffed sweat of men who engaged in aggressive activities such as boxing responded differently to when they smelt the body odour of those using exercise bikes.
Humans may be able to detect the smell of aggression in other people, according to a new study. Body odours from people taking part in aggressive activities such as boxing (stock picture used) triggered a cognitive change in the people smelling it, making them more anxious. This could have its roots in our evolutionary past
Neuroscientists leading the study found those exposed to odours, or chemosignals as they are also called, from the aggressive men became more anxious themselves in response.
Smiljana Mutic, a psychologist at the University Hospital Aachen in Germany and the Monell Chemical Senses Center in Philadelphia, Pennsylvania, who was the lead researcher on the study, said the detection of chemosignals for aggression seems to be subconscious.
They did not find any of the volunteers were able to consciously differentiate between the body odours of the samples they were given.
Miss Mutic, a PhD candidate, said this suggests our ability to detect aggression and anger through body odour may be a hangover from our evolutionary past.
'Seen from an evolutionary perspective, it is extremely beneficial to identify accurately if my counterpart is a source of potential harm to me - also by using the sense of smell,' she said.
'Chemosignals are only one facet of a complex multisensory social communication situation.
'When interacting with somebody, we do not only smell our counterpart, we also hear and feel him or her.
'Most importantly, we see the person.
'Humans dominantly acquire information visually, which leaves less impact for the other senses.
'Humans naturally do not detect those chemosignals consciously.'
To conduct their study, which is published in the journal Chemical Senses, the researchers sampled the body odour of 16 healthy male volunteers taking part in a boxing session and also while using an exercise machine.
Each had been asked to avoid strong smelling foods including garlic, coffee and curry for two days prior to taking part and were also asked to avoid using body scents.
The research suggests humans not only produce chemical signals that indicate when we are feeling aggressive but we can also detect them with our noses (stock picture)
Each of the men had sweat samples taken during the different exercises before having their anger and aggression levels measured through a series of questionnaires and tests.
When the samples were given to 22 other volunteers, their cognitive processing was assessed through a series of tests as they sniffed the samples.
Miss Mutic said the volunteers showed 'heightened levels of anxiety' when exposed to samples from the boxing sessions while body odour from the exercise machines produced no response.
However, she said the team were still to identify exactly which components of body odour are responsible for signalling aggression.
Steroid hormones like testosterone and androstadienone have already been associated with aggression and body odor, for example.
'However, their quantification depends on other non-volatile substances such as the stress hormone cortisol, the mood-dependent neurotransmitter serotonin or the energising hormone adrenaline,' the researchers continued.
'Identifying and quantifying one or several chemical compounds leading to the chemosensory signaling of the aggression process is still an important piece of that puzzle that has not been solved yet.'
The researchers collected sweat from men who took part in a boxing session (stock image pictured) and also when they used an exercise machine. They found the body odour of the men when they were aggressive triggered a response in volunteers sniffing it but the body odour from those using the exercise machine did not
Many animals are thought to communicate mood through smell. Animals like dogs and bears are reputed to be able to smell fear on other animals.
Rats are also thought to be able to smell aggression from intruders.
Humans have also been found to associate certain odours with mood. The smell of tears, for example, seems to convey sadness to others.
As a doctoral researcher in Professor Jessica Freiherr’s research group Neuroscience of Chemosensation, Miss Mutic said it may be why dogs also show such an innate ability to detect our moods - they may be smelling it on us.
She said: 'Humans are considered as the most highly scented apes when it comes to sweat producing glands and body odor.
'But human chemosensory communication research is practically still in the fledgling stage.
'First evidence shows the sense of smell influences the interaction between a baby and it's mother, attractiveness between mating partners or the communication of identity information such as age, gender and health status.
'Further, it has already been shown that other emotional states besides anger, for example anxiety or happiness, can be communicated with the sense of smell.
'Now, if we take into consideration that a dog's olfactory capacities are much better than that of humans, it is perfectly plausible that dogs can identify human aggression chemosignals.'
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