NEW research into how animals bond with each other could shed light on the causes of autism and anxiety disorders, scientists believe.
• If the vasopressin hormone is not working, animals lose 'social memories' and fail to recognise the scent of other individuals
Researchers pinpointed how a key hormone, known as vasopressin, helps animals recognise each other by their smell.
Scientists at the University of Edinburgh found that when the hormone fails to work, animals are no longer able to recognise other individuals from their scent.
Researchers said the study may offer clues about the way humans make emotional connections with each other and deepen our understanding of the role scent plays in memory.
More than half a million people in the UK, including 50,000 in Scotland, suffer from autism.
It is a lifelong development ability affecting the way a person communicates and relates to people around them.
The exact causes are unknown, but it is thought genetics may be partly responsible.
Scientists said the ability to recognise other individuals by smell is said to be crucial for helping animals establish strong bonds with each other.
Edinburgh researchers, working with scientists in Germany and Japan, studied the way rats familiarise themselves with other rats using their sense of smell.
They placed a juvenile rat in an enclosure with an adult rat and left them to sniff each other and interact.
After a short time apart, they put the baby back in the adult's enclosure, together with an unknown baby.
Adult rats whose vasopressin was blocked failed to recognise the baby they had already met.
Scientists concluded that the hormone, already known for its effects on water balance in the body, also helps the brain differentiate between familiar and new scents.
The study did not look directly at human disorders, but it is thought it could shed light on conditions such as some forms of autism and social phobia.
Professor Mike Ludwig, who led the research, said: "This study gives us a window into understanding the biological basis of social interactions.
"Normally, vasopressin supports the forming of 'social memories'. But if it is lost, disturbed, or interrupted then the animals are unable to recognise other individuals by their odour.
"Some studies, including ours, suggest that when the vasopressin system in the brain is not working properly, it may prevent people from forming deep emotional bonds with other individuals, or might underlie conditions such as autism and social phobia."
The study was funded by the Biotechnology and Biological Sciences Research Council.
The organisation's director of research, Professor Janet Allen, said: "Research that helps us to gain a fundamental understanding of how our brains work is vital if we are to know what is happening when something has gone wrong.
"The biological basis of psychological responses can often be extremely complicated, so finding this direct relationship between a hormone and a psycho-social phenomenon could open up a whole wealth of knowledge in this area."
Carol Evans, national director for the National Autistic Society Scotland, said: "While animal research can be useful, it is only a small part of the picture and further research would be required before we fully understand any links to autism.
"More research is needed to help us understand autism and better support the 50,000 people in Scotland living with the condition."
Earlier this month, scientists from the university conducting research into Fragile X Syndrome – a genetic condition that is the leading known cause of autism – discovered that critical phases in the brain's development may be mistimed in some people. Fragile X syndrome affects around one in 4,000 men and one in 8,000 women worldwide.