A Story For You
5/22/22
My mother sometimes tells a funny story about something that my sister, Emma, did as a kid. Everyone at our school wore the same blue sweater as part of the required uniform. One day Emma misplaced her sweater, so my mother took her to the lost and found to pick it back up. In this room full of bins, there was one brimming with identical blue sweaters. Emma’s instinct was to pick up each sweater and give it a deep sniff. She quickly identified one as her own, and then she said, “This one smells like Claire and this one smells like Lucy”. Sure enough, we later learned that her good friends Claire and Lucy had also lost their sweaters, and they matched the ones that Emma identified.
I am rarely satisfied by anecdotal evidence: Did my sister really identify her friends’ sweaters by scent alone? Or was she picking up on subtle visual clues like stains? Or is this a tall tale born of lucky guesses? I did not go into neuroscience with the intention of focusing on questions like this. However, through my six years of training in the neuroscience of human olfaction at a top research institution, I have come to strongly support the conclusion that yes, my sister probably identified her friends by their scents.
Fig. 1.1 Emma Noto (Sweater Sniffer) & Torben Noto (PhD in Olfactory Neuroscience)
I got into neuroscience because I wanted to work on brain-computer-interfaces. One day when I was surfing the web in high school, I came across a video clip of President Obama shaking hands with a quadriplegic person, who was using a brain-controlled robot arm. I instantly knew that I wanted to build robot arms that people could control with their brains.
But as I learned more about neuroscience, I began to understand why topics like olfaction could be much more interesting than they appear on the surface.
My sister’s story sometimes garners the response that she must have a super-human sense of smell. But years of investigation into the social aspects of human olfaction—has taught me a more nuanced view: I think that Emma’s sense of smell is probably average and that most people could perform this feat if they tried. We often think of macrosmatic animals like dogs or rats when we consider olfaction. However, a large body of work has revealed that humans are actually extremely good at smelling (McGann 2017, Zelano & Sobel 2005). We can smell disease on others (Olsson et al. 2007). Mothers can identify their babies by their scent (Porter et al., 1983), and human babies can identify the smell of their mothers by 6 days after birth (Macfarlane, 1975; Schaal et al., 1980). Humans can follow odor trails on the ground (Porter et al. 2007). Humans can smell certain odors at lower concentration thresholds than monkeys and rats (McGann 2017). Odors play a role in how people rate attractiveness and select romantic partners (Mehmet & Croy 2019). Recent work has shown that we naturally, without thinking, constantly, bring our fingers to nose and mouth and covertly sniff them – especially after having touched somebody else (Perl et al. 2020). Unlike dogs, who move their nose and body towards objects to smell them, the human nose points down and is conducive to sampling objects that are brought to the face manually (Jacobs 2019), such as a friend’s blue sweater.
Fig 1.2 Left: A pre-selected frame of a youtube video where people sniffing their fingers are circled. Right: A participant following an odor trail in an olfactory neuroscience experiment. Images from Perl et al. 2020 and Porter et al. 2007.
These are all examples of ‘animal-like’ odor-driven social behaviors in humans that could be used to argue that my sister could indeed identify her friends by their odors. To a neuroscientist, the much more interesting question is: How does her brain know what her friends smell like? How does the brain identify the chemicals that signal safety in food that you eat? How does your brain know to stop breathing if you smell a toxic chemical? Surprisingly little is known about the neuroscience underlying human olfaction and many fundamental questions like these remain unanswered. As evidenced by this story about Emma sniffing a lost sweater, seeking answers to simple questions about olfaction can lead to profound new understandings of how the brain works.