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Does the Nose Know? How Animals Detect Fear

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Although I’ve never personally come face-to-face with an angry bear or an aggressive crocodile, I’d like to think that I’d know what to do if I did; I’d defuse the situation by staying perfectly calm, because as everyone knows, animals can smell fear. Or can they?

This peculiar bit of conventional wisdom would have us believe that not only are animals’ olfactory receptors so sensitive that they can actually smell a human emotion, but also that emotions themselves leave physical and chemical trails. Even though dogs have noses that are up to 100,000 times more sensitive than humans’, the notion of any animal actually “smelling” fear is little more than an old wives’ tale.

The frightening dog you encounter on your morning walks (or that hypothetical angry bear) can’t actually smell your emotions, but it’s true that he can probably sense them. Animals communicate with each other mostly nonverbally, so they become expert readers of body language. They don’t smell fear, they sense it by interpreting bodily cues, and they can sense it in other animals as well as in humans. They look for quick, darting gestures, nervous behaviors like rapping or tapping, tensing the body, or an inability to make eye contact. Detecting signs of fear is vitally important in the wild, because an anxious or stressed animal is capable of attacking or engaging in other unpredictable behavior. Each species evolved to be able to quickly and accurately read other animals in order to ensure its own safety at all times.

Our companion animals such as dogs and cats may not have to worry about predators, but they still retain the ability to sense fear, especially in their humans. In fact, they’re experts at detecting just about any emotion, because they’re not just experts at body language, but at their owner’s body language in particular. Pet parents love to brag about how their cat “always knows just when I need comforting” or how their dog “always picks the right moment to cheer me up.” These are examples of companion animals reading their owners’ emotions using body language clues. A dog or cat can’t instinctively know whether his or her owner has just lost a job, or whether that stranger at the door has a nefarious purpose, but they can interpret visual signals from our own behavior—whether or not we even know we’re giving them off at all.

Part of a normal stress response may include sweating or the release of certain pheromones, so it may be possible for one animal to use its sense of smell to interpret the emotional state of another, just as animals interpret each other’s age, sex, and reproductive status. However, pheromone communication only functions within a single species, and there’s little evidence that humans give off pheromones at all.

Animals can no more “smell fear” than humans can “smell a rat” or “smell victory,” but in case you ever meet that angry bear, staying calm and relaxed is probably still some pretty good advice.


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