Saturday, October 3, 2015

The Alleged Limitations of Olfactory Language

That smells can be difficult to name is a commonplace observation. Almost as commonplace as the observation that there exist many specialized vocabularies for smell, such as those used by perfumers, wine tasters, brewers, coffee roasters, tobacconists, potheads, etc., etc. In this battle of off-setting banalities, those who downplay our ability to verbalize odors are often ceded the victory, in keeping with the pessimistic Greco-Freudian view that the human sense of smell is a poor thing, rendered vestigial from lack of use, and substantially inferior to that of other animals.

A more optimistic view is that humans are quite competitive in terms of odor sensitivity (often exceeding that paragon of scent detection, the dog) and that a remarkable amount of information regarding other people (emotional, physiological, and health status, for example) is received and processed via the nose. This positive outlook has been gaining support steadily in recent years but science journalists and assistant beauty editors have been slow to recognize the trend. This is not surprising; they are, after all, science journalists and assistant beauty editors. What is surprising is that a pair of credible scientists have now thrown in with the nasal nay-sayers and offered a theoretical account of why humans must necessarily suck at naming smells.

That might seem a rather rude way to characterize a paper decorously titled “The muted sense: neurocognitive limitations of olfactory language,” but I think it captures the essence of what Jonas Olofsson and Jay Gottfried are attempting to do.

Olofsson and Gottfried begin with three papers from the 1970s that find when you bring people into a psychology lab and have them sniff odors absent any contextual information (visual, auditory, or otherwise), they have a hard time coming up with the correct name. Provide them multiple-choice odor names and they generally choose the correct one. For good measure, Olofsson and Gottfried also reference studies showing that under similar laboratory conditions people suck at picking out individual components from a bouquet of scents.

Atop these rudimentary observations, O&G construct a “biologically informed framework for olfactory lexical processing.” Being neuro-imaging specialists, they sketch connections between piriform cortex, orbitofrontal cortex, and all the other neuroanatomical waystations on the route from nostril to naming. You will enjoy the discussion if this sort of thing appeals to you:
Importantly, odors are already integrated with lexical representations at the third synapse from receptor neuron input. This could put olfaction at a disadvantage compared with the visual system, where multiple subcortical and cortical sites create object representations before lexical–semantic integration by integrating features at different spatial scales.
My concern here is not with O&G’s theoretical edifice, but with their presumption that the difficulty in generating a verbal tag for a context-free odor is somehow fundamental to our understanding of human olfaction, and with their view that this phenomenon benefits from a convoluted account drawing upon “recent behavioral and neuroimaging data.”

Take the laboratory task upon which their entire argument is based: could there be anything more remote from the universal, everyday experience of smell than being confronted with a sniff-bottle and asked to name its contents by smell alone? What real world setting does this resemble? The answer is none.

Smells always occur in a context, and it is only within this context that we try to make sense of them. At the fish market, for example, we sniff to see whether the fish is fresh. Whether we can summon up the name “trimethylamine” is irrelevant. Smells may confirm our visual expectations (“it seems to have rained here recently”) or draw our attention to something that warrants exploration (“what’s burning?”) all without resort to specific lexical representations.

Tagging a smell with a specific lexical term requires high-level abstraction. In contrast, odor identification and description are broader abilities that are exercised more often and with greater functional impact. When olfactory naming happens in real life it also happens in a natural context and the language processing is tuned to an appropriate (and useful) level of generalization. Here’s a non-laboratory example of olfactory language in action:
“Umm. Is someone grilling dinner?”
“Yeah, it smells like hamburgers.”
To me, that is an example of rapid, precise, and biologically useful neurocognitive olfactory processing. But in Olofsson and Gottfried’s model it simply doesn’t exist.

In my view, the O&G model is an elaborate neurocognitive account of a laboratory artifact. It has little bearing on the broader role of olfaction in human behavior and communication. Does this sound extreme? Then ask yourself: does the near-universal inability to name the musical key of a song imply that “people are poor at describing sounds?”

The study discussed here is “The muted sense: neurocognitive limitations of olfactory language,” by Jonas K. Olofsson & Jay A. Gottfried, published in Trends in Cognitive Sciences, 19:314-321, 2015.

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