Stress in humans can affect how optimistic dogs
feel, research suggests
================================================

The ability of dogs to sniff out stress levels
in humans has been known for some time.

But the relationship between woman and man's
four-legged best friend is two-way, and
scientists now believe they have discovered that
when a dog senses a person in distress, it has a
knock-on effect in the behaviour of the animal -
most notably, it makes them pessimistic.

New research is believed to be the first to test
how dog owners' emotional states can affect
their pets.

Dr Nicola Rooney, senior lecturer at the
University of Bristol's veterinary school and
lead author of a paper on the subject, said:
"Dog owners know how attuned their pets are to
their emotions but here we show that even the
odour of a stressed, unfamiliar human affects a
dog's emotional state, perception of rewards and
ability to learn.

"Working dog handlers often describe stress
travelling down the lead, but we've also shown
it can also travel through the air."

She added that understanding how human stress
affects dogs' wellbeing was important for dogs
in kennels and training companion, working and
assistance dogs.

The team used a test of "optimism" or
"pessimism" in animals to determine whether they
were feeling positive or negative emotions after
exposure to people's stressed and relaxed
odours.

The researchers recruited 18 dog-owner
partnerships to take part in trials in which
dogs were trained that when a food bowl was
placed in one location it contained a treat but
when placed in another location it was empty.

Once dogs learned the difference between these
bowl locations, they were faster to approach the
location with a treat than the empty location.
Researchers then tested how quickly the dog
would approach new, ambiguous bowl locations
positioned between the original two.

A quick approach reflected optimism about food
being present in these ambiguous locations - a
marker of a positive emotional state - while a
slow approach indicated pessimism and negative
emotion. These trials were repeated while each
dog was exposed to either no odour or the odours
of sweat and breath samples from humans who were
feeling stressed from a maths test or relaxed
after listening to soundscapes.

Researchers discovered that the stress smell
made dogs slower to approach the ambiguous bowl
location nearest where they had been trained to
expect empty bowls. This effect that was not
replicated after exposure to the relaxed smell.

These findings suggest that the stress smell may
have increased the dogs' expectations that this
new location contained no food, similar to the
nearby empty bowl location. The researchers
suggested this could be a way for the dog to
conserve energy and avoid disappointment.

The team also found that dogs continued to
improve their learning about the presence or
absence of food in the two trained bowl
locations and that they learned the difference
faster when the stress smell was present.



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