Humans may have a stronger sense of smell than dogs; here’s why

It’s a widely held belief that dogs possess a sense of smell that far exceeds human capabilities, with their super-sensitive noses able to detect an array of odours imperceptible to us. 

However, if content creator Krish Ashok were to go by, contrary to popular belief, the human nose may outperform our four-legged friends. In a reel posted on Instagram recently, he says, “Dogs and most of the animals are fantastic at smelling things from the outside. In fact a dog’s head with its long snout is designed to smell the smallest trace of some molecules. But here’s the catch, dogs do not smell very well as they breathe out.”

 

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How does the human sense of smell compare to that of dogs?

Dr Manoj Mishra, senior consultant ENT at Max Super Speciality Hospital, Lucknow, says, “Humans and dogs have significantly different olfactory capabilities due to anatomical and functional differences. Dogs are known for their extraordinary sense of smell, with about 300 million olfactory receptors compared to humans’ 6 million. Additionally, the part of a dog’s brain devoted to analysing smells is proportionally 40 times larger than that of a human. This allows dogs to detect scents at concentrations up to 100,000 times lower than humans can.”

However, he agrees with Ashok, citing recent research that has shown that the human sense of smell is more powerful than previously thought. Humans can discriminate between one trillion different odours, which is far more than the previously estimated 10,000. 

“While dogs are superior in detecting certain types of scents, such as those associated with tracking or detecting substances like drugs or explosives, humans have been shown to be more sensitive to specific odours relevant to our survival and daily life, such as those related to food and environmental hazards,” he states. 

What is retronasal olfaction?

Retronasal olfaction, Dr Mishra says, refers to the detection of odours when breathing out during eating and drinking, which occurs when odorants from food in the mouth travel through the nasopharynx to the olfactory epithelium in the nose.

This process significantly enhances the perception of flavour, as it combines with taste receptors on the tongue to create the full flavour experience. Retronasal olfaction allows humans to detect a complex array of flavours and aromas in food, making it a critical aspect of our culinary experiences and appreciation of different tastes.

For individuals who are unwell, foods like khichdi or chicken soup are more palatable because they often have strong, comforting flavours and aromas (Source: Freepik)

Some factors that contribute to the superior ability of human noses to discern specific aromas

Several factors contribute to humans’ ability to discern specific aromas, according to Dr Mishra:

Olfactory Bulb and Cortex: The human olfactory bulb, though smaller than that of dogs in absolute terms, is highly efficient in processing a vast range of odors due to its complex neural connections.

Number of Receptors: Humans possess about 400 different types of olfactory receptors, allowing for the detection of a wide variety of chemical compounds.

Cultural and Cognitive Factors: Humans also benefit from a rich cultural context and cognitive ability to categorise and describe smells, enhancing our ability to differentiate between complex scents such as spices in food.

The effect of a blocked nose on the perception of taste and flavour

Dr Mishra elaborates, “A blocked nose can significantly impair the sense of smell, which in turn affects the perception of taste and flavour. This is because a large part of what we perceive as taste actually comes from our ability to smell through retronasal olfaction. When the nasal passages are blocked, the pathway for these odorants to reach the olfactory receptors is obstructed, dulling the overall flavour experience.”

Interestingly, he shares that for individuals who are unwell, foods like khichdi or chicken soup are more palatable because they often have strong, comforting flavours and aromas that can still be detected even with a reduced sense of smell. “These foods are also generally easy to digest and can be soothing to the stomach, providing nourishment without overwhelming the senses.”

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