Odor knowledge, odor naming, and the “tip-of-the-nose” experience

The present chapter concerns odor naming. In particular, it focuses on our naming ability and what we know about odors, in terms of both objective and subjective (metacognitive) knowledge, when we cannot name them. Our ability, or perhaps more aptly, our inability, to correctly name odors without the help of visual or other contextual cues has vexed researchers of olfaction for decades. It has even been described as the “most contentious issue in human olfactory processing” (Herz & Engen, 1996, p. 301). Imagine that you look at a lemon, that you have no other input apart from the visual, and are asked to tell its name. You will likely not find it difficult to tell that it is a lemon, as would all healthy observers. If you instead smell the odor of lemon (again without any other sensory input), naming performance drops considerably, even though the odor will feel very familiar. The environment is full of items that anyone within a given culture would name correctly if they see the object, but if they only smell it, the task becomes considerably more difficult. We still do not fully understand why this is so. In the present chapter, we will present some of the main ideas about why it is so difficult to name odors. We will also examine the relatively few studies that have investigated “feelings of knowing” for odors that you cannot name. Our Ability to Name and Identify Odors If you let a group of participants try to name a set of familiar everyday odors without the help of other cues, naming performance rarely exceeds 50 percent (e.g., Cain, 1979, 1982; Cain, de Wijk, Lulejian, Schiet, & See, 1998; Desor & Beauchamp, 1974; de Wijk & Cain, 1994a, 1994b; de Wijk, Schab, & Cain, 1995; Distel & Hudson, 2001; Lawless & Engen, 1977; Olsson & Fridén, 2001). For unfamiliar and uncommon odors, naming performance is considerably lower, and successful naming of any single item, however common, rarely reaches 100 percent across a group of participants. Note that these performance levels pertain to our ability to correctly name odors presented in a laboratory environment and in the absence of other contextual cues. In everyday life, we often have other cues that help us tell what odor we smell.