New Study Finds Dog Can Smell Human Stress And It Affects Their Decision-Making Process

A new research suggests that dogs can smell human stress, and it affects their emotions and decision-making process, which then leads them to making negative decisions.

While previous studies have revealed that dogs can indeed smell human stress, the effect it has on them hasn’t been studied yet.

The study, published on Scientific Reports on July 22, involved using odor samples from different people during stressful and relaxing activities and letting dogs sniff the odors and see how they would react to the scent of stress.

Dr. Zoe Parr-Cortes, a veterinarian and Ph.D. student at Bristol Veterinary School and the lead author on the study tells WLIW-FM, “Some people have looked at, can dogs actually detect differences in odor. And they have. But nobody had really looked at how that affects the dog’s emotions.”

The human volunteers were put through a stress test and were later rewarded with relaxation time. And their odor samples were collected by sticking pieces of cloth under their armpits during both test.

It also involved 18 dogs that were put under their own test. The dogs were trained to learn that a food bowl on one side of the room always had a food reward (referred to as a “positive” location in the study), while the other was always empty (referred to as a “negative” location).

Over time and expectedly, the dogs approached the bowl with food in it.

The researchers then removed the two bowls in their locations and created an “ambiguous” location in the middle.

The dogs’ owners then opened a jar using one of the rags with odor samples and had the dog sniff it, before a bowl was put in front of them.

“Do they approach quickly, optimistic that there’s going to be a food reward in there, or do they approach more slowly, with a more pessimistic outlook that there might not be food in that bowl?” Parr-Cortes says of the dogs.

Researchers ran this test many times, with both stressed and relaxed odor samples and in different orders.

After the test, they found that the relaxed scent didn’t yield much of a result. However, when the dogs smelled the stress odor, they became more hesitant to approach the bowl in the ambiguous location, meaning they were a lot pessimistic that the bowl had any food in it.

Parr-Cortes explains, “It basically shows that the stress smell might affect how [dogs] respond to ambiguous situations. They might be less likely to try something risky if they think they’re going to be disappointed.”

The researchers concluded that these findings may indicate that human odor can affect how a dog perceives risks and rewards.

Molly Byrne, a Ph.D. student at Boston College who studies comparative cognition but isn’t affiliated with the study thinks the same way too and was impressed with the new findings.

She said that dogs think a reward is less likely to come if their owner is in a bad mood, which makes a lot of sense. “When your owner is training you, they’re probably not giving you maybe as many treats if they’re really stressed.”

“These findings highlight the need to consider dogs’ training and working environments from an olfactory perspective,” the researchers wrote.