The fact that we sometimes have no verbal label for odors yet can recognize and respond to them appropriately suggests that our ability to perceive odors does not require language. This may not seem very important, but when we think about vision we notice that as soon as we look at something we automatically have a name for it in our minds. In fact, we are incredibly verbal creatures and, without necessarily being aware of it, we tag almost all our sensory experiences with words. However, this is not the case with our sense of smell. We often experience odors wholly and completely without assigning any verbal codes to them. Additionally, when words come along with an odor, our perception of smells gets re-routed into our verbal circuits and to some extent ceases to be completely olfactory.
An example of the strong effect of words on ordinary olfaction is how easily odor illusions can be created verbally. The first demonstration was recorded in 1899 by Emory Edmund Slosson, a professor of chemistry at the University of Wyoming. During a lecture he stated that he wished to see how rapidly an odor would be diffused through the air and requested the audience to raise their hands as they smelled it. He poured distilled water over cotton explaining that it was a chemical with a strange odor that nobody would have smelled before. Slosson claimed that within 15 seconds most of the front row had raised their hands and within one minute three quarters of the class had their hands up! More recently, in 1978, Michael O’Mahony, a professor of food sciences at the University of California, Davis, conducted a publicized and very impressive olfactory illusion with great effect. On a British television and radio station he had it announced that a certain sound frequency would produce the perception of a particular outdoorsy smell (no smell was actually named). From this mere suggestion and a set of beeps that were broadcast, he was able to get hundreds of people calling into the TV and radio station saying that they could smell something. Specific scents varied from manure to honey, and in some cases people even reported feeling dizzy, having a coughing fit, or experiencing a bout of hay fever!
It is also possible to create olfactory illusions by calling one and the same odorant by two different names. Herz (2005) gave participants a set of odorants to evaluate at two different sessions separated by one week. At each session the odorant was given a different verbal label, either positive or negative. For example, the odorant mixture of iso-valeric + butyric acid was either called “vomit” or “Parmesan cheese.” The different verbal labels caused the participants’ evaluation of the odors to be dramatically different and in each case in accord with the name’s connotation of the odor. When the odorant was called “Parmesan cheese” participants indicated high liking for it and said they would eat it, and when the exact same chemicals were called “vomit,” participants indicated strong disgust and said they wanted to run out of the room. Moreover, during debriefing, participants wouldn’t believe that the two odors with the different names were actually the same chemical compound.
This would never happen with vision. If someone waved their hand in the air and said “Now who can see the white rabbit?” you would not think that if you squinted hard enough you could see a white rabbit—you would think that person was crazy. Although we sometimes “think” we are seeing things in visual noise that are in fact not there (such as Jesus in a piece of toast) this is more a misextrapolation from reality rather than a complete fabrication. The reason we can be so gullible with odors is because they are invisible and we are obsessed with figuring out what things are, so we look to external cues for help. If the situation or environment has a plausible answer, we may emphasize it rather than relying on the smell itself. Another point to take home is that context—a mental state, physical situation, or environment that induces a set of preconceptions and expectations—has an enormous influence on odor perception, much more so than it has on our other sensory systems.
Herz, R. S. (2005). The unique interaction between language and olfactory perception and cognition. Trends in Experimental Psychology Research. (pp. 91–109). New York: Nova Science Publishers, Inc.