Even the friendliest dog can show aggression towards a person it dislikes. But how do dogs "choose" such people? Are they irritated by the smell? Or perhaps it is intuition?
Even dog owners sometimes cannot understand why their pet does not show affection towards someone. In some cases, the reason is obvious: for example, the animal may not tolerate a certain smell or may be afraid of objects that the person is holding. However, more often than not, it remains a mystery.
Scientists have long been trying to unravel this mystery. Since 2005, biologists have begun to actively study dog behavior, which has allowed for a deeper understanding of how these animals perceive information about people and determine whether to be angry with them.
The Sense of Smell in Dogs is a True Superpower
Humans have about five to six million olfactory receptors, while dogs have 220 million, and some breeds even have 300 million. Dogs are capable of detecting scents that are only noticeable to humans at concentrations 50 times higher. In some cases, the scent must be 100 times more concentrated before a human can detect it.
Studies using magnetic resonance imaging (MRI) have shown that dogs lack a large frontal lobe, as humans do. Instead, they have a massive olfactory bulb that occupies 10% of their brain.
Since a dog's sense of smell is 10,000, and sometimes even 100,000 times better than ours, they are able not only to detect scents that are undetectable to the human nose but also to assign special significance to them. While we typically do not analyze smells, dogs gather and remember information about them.
Sometimes this leads to strong associations. For example, a small study showed that a dog reacted aggressively only to those people who had eaten pizza before going outside. The pet continued to sense the smell of the treat even hours later.
The reason for this was that, in puppyhood, a pizza delivery person kicked the dog, which created a negative association with the smell of pizza and danger. Understanding this connection allowed a behaviorist to retrain the dog to associate that smell not with a threat but with pleasant moments — for example, the opportunity to try a piece.
Emotions Also Have a Smell
Research shows that dogs can detect the scents of various human emotions due to changes in chemical signals, such as adrenaline, sweat, and body odor.
In a 2018 study, scientists collected sweat from pet owners while watching comedies and horror films. Dogs were randomly assigned to groups sniffing either “scary” or “happy” sweat. As a result, it was found that dogs that sniffed “fear” were more focused on their owners and more likely to react to their stress.
Other studies have shown that dogs can sense changes in the fight-or-flight response, including changes in facial expressions and gestures.
Thus, when a dog assesses whom to bite or bark at, it relies on its sense of smell. It may dislike a specific scent and the association with it, or the dog may sense that the person is feeling fear or is in a state of high stress.
