Human stress ‘makes dogs more pessimistic’

A new study has indicated that dogs make more “pessimistic” choices when they are exposed to the scent of human stress.

Researchers at the University of Bristol believe their findings highlight the need for greater awareness among veterinary professionals about the extent to which they can affect their patients.

The paper, published in the Scientific Reports journal, is thought to be the first to indicate that olfactory indicators can have an impact on canine responses.

Eighteen dogs and their owners were recruited to take part in a series of trials in which they learned bowls contained a treat in one location but not in another.

Exposed

Sweat and breath samples were also collected from 11 human volunteers in stressed and relaxed states, which the dogs were then exposed to in further trials including tests where bowls were positioned in ambiguous positions.

The paper said each sample volunteer was told to avoid “spicy foods, intense exercise, using body wash, perfume, deodorants or antiperspirants” on test days, as well as to avoid eating for an hour prior to testing and either smoking or drinking alcohol for at least 12 hours prior to testing.

The researchers found the human stress odour “significantly decreased” dogs’ likelihood of approaching an ambiguous site in a manner that was not observed with the relaxed odour.

They also reported that differences across the training locations only became substantial when the stress odour was present.

The paper said that because the odours were from people who were not familiar to the canine participants, the results suggested they “may detect and respond to an olfactory ‘stress signal’ shared across humans rather than responding to a familiar odour with a learned response”.

It continued: “These findings may indicate an effect of human odour on the emotional state of dogs and of how dogs perceive risks and rewards.”

Primary researcher Zoe Parr-Cortes, a PhD student at the Bristol vet school and a registered clinician, said the findings showed how far humans can impact both dogs’ moods and health.

While the research team are also keen to look at the effects of both repeated exposure to stress odours and other emotions in the future, she said the current findings indicated that keeping calm or engaging in a relaxing activity before interacting with dogs could reduce the effects observed.

She added: “Having been a vet in practice myself, I know this is easier said than done. But we think it’s important to be aware of how our emotions may impact dogs.”

Implications

Lead author Nicola Rooney, a senior lecturer in wildlife and conservation, said the implications of the study also go far beyond veterinary practice.

She said: “Understanding how human stress affects dogs’ well-being is an important consideration for dogs in kennels and when training companion dogs and dogs for working roles, such as assistance dogs.

“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 shown it can also travel through the air.”