“Rather than being weak and vestigial, human smell appears to be quite powerful. Some have even suggested that humans and their primate relatives are “supersmellers” among animals. It is time, therefore, for a new appreciation of this much maligned and neglected sense.”—Gordon Shepherd
The featured book this week is Neurogastronomy: How the Brain Creates Flavor and Why It Matters, by Gordon Shepherd. The following is an excerpt from chapter 1, The Revolution in Smell and Flavor:
Given this importance of the flavors we learn to like, it seems to me remarkable, and unfortunate, that most people are unaware that the flavors are due mostly to the sense of smell and that they arise largely from smells we detect when we are breathing out with food in our mouths. Few people know how modern research shows that an odor sets up patterns of activity—“smell images” in our brains— that are the main basis for our perception of flavors. These smell images are hidden factors that determine most of the plea sure we get from eating, and they share the blame for the problems we incur when eating foods that are not good for us. If we can understand better the central role that smell plays, we can understand better how to reduce the problems and increase the joy.
To appreciate the importance of retronasal smell in our lives, let’s step back and look at how far we’ve come in changing ideas that go back to the ancient Greeks.
Most people regard the sense of smell as not very important. The legacy of thinking of smell in this way began with Aristotle. In discussing the senses in De Anima (On the Soul), he observed that “our sense of smell is inferior to that of all other living creatures, and also inferior to all the other senses we possess.”
If you’re laboring under this misapprehension 2,500 years later, you’re not the only one. Like almost everyone else, you probably enjoy pleasant scents, such as attractive perfumes, fragrant flowers, and a steak barbecuing on the grill, and you do not like unpleasant smells, such as body or bathroom odors and polluted air. And that is about the limit of how much regard you give to smell.
These impressions seem minor compared with the important roles played by our sight and hearing. Against these, smell can seem trivial, although not if you suddenly lose your sense of smell because of an accident or infection. In her book Remembering Smell: A Memoir of Losing— and Discovering— the Primal Sense, Bonnie Blodgett has described the devastating loss of flavor that may occur. Most of that loss is due to retronasal smell. Still, if forced to give up one of the senses, who would choose a life without vision or hearing rather than smell? Sight and sound are obviously the essential senses for normal living and use of language.
But this is putting the question in the wrong way. What are the factors that shape our daily behavior? Which inputs to our brains are the motivating forces that determine the quality of our daily lives and that influence the decisions we make about health, diet, mates, and social relations? If we stick with only our obvious sensations, we miss the deeper factors. Among them, smell plays powerful but hidden roles.
As discussed in the Introduction, the new evidence regarding these roles for smell comes from work in many fields. Taken together, all these studies reflect how the sense of smell and associated flavor engage an astounding extent of the human brain. This work is not only intriguing to the general public, but involves profound insights into our biological nature. Many research workers are realizing that the sense of smell is ripe for investigation as one of the most exciting frontiers in the brain. They are intrigued that this system may hold the key to unlocking many of the secrets of our body. This was already realized de cades ago by the physician and essayist Lewis Thomas: “I should think we might fairly gauge the future of biological science, centuries ahead, by estimating the time it will take to reach a complete, comprehensive understanding of odor. It may not seem a profound enough problem to dominate all the life sciences, but it contains, piece by piece all the mysteries.”
One of those mysteries is how the brain uses smell to create flavor.
Current studies are already revealing capabilities of human smell that go far beyond the traditional view. Rather than being weak and vestigial, human smell appears to be quite powerful. Some have even suggested that humans and their primate relatives are “supersmellers” among animals. It is time, therefore, for a new appreciation of this much maligned and neglected sense. The aim of this book is to show how the real power of human smell lies in its key role in human flavor.