Jonas K. Olofsson and Jay A. Gottfried, ‘The Muted Sense: Neurocognitive Limitations of Olfactory Language’, Trends in Cognitive Sciences, 19 (2015), 314-21.

In this paper an idea that seems to be quite well-established – that we are less good at naming the things we smell than the things we see – is given a neuroscientific spruce-up. Olofsson and Gottfried present a neural foundation for the phenomenon.
      One reason why we are not very good at naming odours may be that our brains encode the smell as a single unit. We are able to identify visual objects by features and parts – a particular kind of ears, a particular kind of tail, a colour, bring the name ‘fox’ pretty quickly – but we can’t do that with smells so easily.
      However, Oloffson and Gottfried think that the key problem is that the olfactory system in the brain doesn’t connect with verbal systems in the same way that the visual system does. When we see something, they argue, on the basis of imaging experiments, ‘a rich network of cortical connections enables parallel and iterative access to feature-selective detail, allowing the assembly of richly endowed visual object configurations and, critically, offering multiple entry points into the lexical-semantic network’.
      Whereas when we smell something, the issue of ‘valence’ – attractiveness or aversiveness – comes in very strongly, and emotional encoding seems to drown out the possibilities of articulation. As they say, ‘olfactory objects are endowed with emotion, value, memory, and experience… the ability to enrich these configurations with lexical-semantic content is relatively meagre. This limitation poses an initial challenge to generating odour names’. Another way of putting this: ‘olfactory representations might thus be conducted to the language network in an unconstrained, indeterminate format, causing unspecific activation of latent object concepts’
      The article takes an interesting turn towards cultural differences, because of course it’s worth asking whether this is a phenomenon of particular cultures. They cite research carried out among nomadic hunter-gatherers in the Malay peninsula. Although the Jahai language handles smells quite differently, ‘odour naming accuracy… was well below colour naming accuracy in English’, and this is ‘compatible with the notion that olfactory object naming is limited’.

*

I want to do something with this, because it seems to me that the link between smell and articulation might be something that arises interestingly in literature. I suppose there may not be lots of illuminating moments when someone asks ‘what’s that smell?’ – but I’d be happy to hear about them. There may also be a question about whether it’s legitimate to take naming failure into a more general struggle to describe odours, but the Oloffson and Gottfried paper suggests that it is.
      So, as a first literary instance of the phenomena addressed in the scientific literature, I offer a moment in D.H. Lawrence’s short story ‘Odour of Chrysanthemums’. At this point in the story, a mother suspects that her husband is out drinking, hence the sardonic tone:

The child put the pale chrysanthemums to her lips, murmuring:
‘Don’t they smell beautiful!’
Her mother gave a short laugh.
‘No,’ she said, ‘not to me. It was chrysanthemums when I married him, and chrysanthemums when you were born, and the first time they ever brought him home drunk, he’d got brown chrysanthemums in his button-hole.’
She looked at the children. Their eyes and their parted lips were wondering. The mother sat rocking in silence for some time.

Her description of the quality of the chrysanthemum smell delivers exactly the ’emotion, value, memory’ mentioned above. The child’s invitation to consider the smell as a smell, to make ‘beautiful’ more specific, elicits a precise autobiographical account. Of course, the mother’s memory is not only prompted by an olfactory experience, but it still suggests a literary awareness of the constraints on the language of smell.
      Thanks to this interesting site it is easy to compare this version of the story (from The Prussian Office and Other Stories, 1914) with Lawrence’s earlier drafts. In the uncorrected proofs of 1910, and the English Review text of 1911, the mother’s speech is slightly different:

‘Hateful!’ she said. ‘I hate them. It was chrysanthemums when I married him, and chrysanthemums when you were born, and the first time they ever brought him home drunk he’d got brown chrysanthemums in his coat. When I smell them I could always think of that, me dragging at him to get his coat off.’

This is the proof version. The extra sentence at the end is also in the English Review, though in that version the more emphatic beginning is removed. It’s interesting that Lawrence subsequently removed the most explicit description of the evocative power of smell. The 1914 version is very effective in its understatement; we know, perhaps, that she is trying to protect herself from a rush of emotional associations.